diff --git a/assets/swagger.json b/assets/swagger.json
index e08625e82907c..7bd7db96c8b0a 100644
--- a/assets/swagger.json
+++ b/assets/swagger.json
@@ -5678,6 +5678,9 @@
         "uiCssURL": {
           "type": "string"
         },
+        "uiDefaultTheme": {
+          "type": "string"
+        },
         "url": {
           "type": "string"
         },
diff --git a/docs/operator-manual/argocd-cm.yaml b/docs/operator-manual/argocd-cm.yaml
index 00760415a48fd..763b41676c8b5 100644
--- a/docs/operator-manual/argocd-cm.yaml
+++ b/docs/operator-manual/argocd-cm.yaml
@@ -310,6 +310,14 @@ data:
   # - Files may also be loaded from remote locations via fully qualified URLs.
   ui.cssurl: "./custom/my-styles.css"
 
+  # The default theme for the UI. This theme will be applied when users first access the UI.
+  # Users can still change their theme preference, which will be stored in their browser localStorage.
+  # Valid values: "light", "dark", "auto"
+  # - "light": Light theme (default if not specified)
+  # - "dark": Dark theme
+  # - "auto": Automatically match the user's system preference
+  ui.defaulttheme: "auto"
+
   # An optional user-defined banner message that's displayed at the top of every UI page.
   # Every time this is updated, it will clear a user's localStorage telling the UI to hide the banner forever.
   ui.bannercontent: "Hello there!"
diff --git a/docs/operator-manual/ui-customization.md b/docs/operator-manual/ui-customization.md
index 6569d1fa6b6be..83b738af70733 100644
--- a/docs/operator-manual/ui-customization.md
+++ b/docs/operator-manual/ui-customization.md
@@ -1,5 +1,19 @@
 # UI Customization
 
+## Default Theme
+
+You can configure the default theme for the ArgoCD UI by setting the `ui.defaulttheme` key in the [argocd-cm](argocd-cm-yaml.md) ConfigMap.
+
+The following configuration:
+```yaml
+ui.defaulttheme: "auto"
+```
+
+**Behavior:**
+- First-time users will see the theme specified in `ui.defaulttheme`
+- Existing users will continue to see their previously selected theme (stored in browser localStorage)
+- Users can change their theme preference at any time, which will be persisted in their browser
+
 ## Default Application Details View
 
 By default, the Application Details will show the `Tree` view.
diff --git a/pkg/apiclient/settings/settings.pb.go b/pkg/apiclient/settings/settings.pb.go
index ec1015c6f4b48..c15ca6342a500 100644
--- a/pkg/apiclient/settings/settings.pb.go
+++ b/pkg/apiclient/settings/settings.pb.go
@@ -99,6 +99,7 @@ type Settings struct {
 	UiBannerPosition          string                             `protobuf:"bytes,20,opt,name=uiBannerPosition,proto3" json:"uiBannerPosition,omitempty"`
 	StatusBadgeRootUrl        string                             `protobuf:"bytes,21,opt,name=statusBadgeRootUrl,proto3" json:"statusBadgeRootUrl,omitempty"`
 	ExecEnabled               bool                               `protobuf:"varint,22,opt,name=execEnabled,proto3" json:"execEnabled,omitempty"`
+	UiDefaultTheme            string                             `protobuf:"bytes,30,opt,name=uiDefaultTheme,proto3" json:"uiDefaultTheme,omitempty"`
 	ControllerNamespace       string                             `protobuf:"bytes,23,opt,name=controllerNamespace,proto3" json:"controllerNamespace,omitempty"`
 	AppsInAnyNamespaceEnabled bool                               `protobuf:"varint,24,opt,name=appsInAnyNamespaceEnabled,proto3" json:"appsInAnyNamespaceEnabled,omitempty"`
 	ImpersonationEnabled      bool                               `protobuf:"varint,25,opt,name=impersonationEnabled,proto3" json:"impersonationEnabled,omitempty"`
@@ -298,6 +299,13 @@ func (m *Settings) GetExecEnabled() bool {
 	return false
 }
 
+func (m *Settings) GetUiDefaultTheme() string {
+	if m != nil {
+		return m.UiDefaultTheme
+	}
+	return ""
+}
+
 func (m *Settings) GetControllerNamespace() string {
 	if m != nil {
 		return m.ControllerNamespace
@@ -780,90 +788,91 @@ func init() {
 func init() { proto.RegisterFile("server/settings/settings.proto", fileDescriptor_a480d494da040caa) }
 
 var fileDescriptor_a480d494da040caa = []byte{
-	// 1318 bytes of a gzipped FileDescriptorProto
-	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0xa4, 0x56, 0x4d, 0x6f, 0x1b, 0x37,
-	0x13, 0x86, 0x22, 0xc7, 0x96, 0xc6, 0xb1, 0x65, 0x33, 0x8e, 0xb3, 0xd1, 0x9b, 0xd8, 0x7a, 0x75,
-	0x08, 0xd4, 0xa2, 0x5d, 0xc5, 0x36, 0xfa, 0x81, 0xa0, 0x41, 0x6b, 0x49, 0x41, 0xa2, 0xc6, 0x49,
-	0x5c, 0x26, 0x4e, 0x81, 0x5e, 0x02, 0x7a, 0x77, 0x2a, 0x6d, 0xbd, 0x22, 0x17, 0x24, 0x57, 0x89,
-	0x72, 0xec, 0x0f, 0xe8, 0xa5, 0xfd, 0x21, 0x3d, 0xf7, 0x5e, 0xb4, 0xc7, 0x02, 0xbd, 0x1b, 0x85,
-	0xd0, 0x1f, 0x52, 0x2c, 0xf7, 0xc3, 0xeb, 0x95, 0x9c, 0x16, 0xc8, 0x8d, 0x7c, 0x9e, 0xf9, 0xe2,
-	0x70, 0x86, 0x1c, 0xd8, 0x52, 0x28, 0xc7, 0x28, 0xdb, 0x0a, 0xb5, 0xf6, 0xf8, 0x40, 0x65, 0x0b,
-	0x3b, 0x90, 0x42, 0x0b, 0xb2, 0xe4, 0xf8, 0xa1, 0xd2, 0x28, 0xeb, 0x1b, 0x03, 0x31, 0x10, 0x06,
-	0x6b, 0x47, 0xab, 0x98, 0xae, 0xdf, 0x1c, 0x08, 0x31, 0xf0, 0xb1, 0xcd, 0x02, 0xaf, 0xcd, 0x38,
-	0x17, 0x9a, 0x69, 0x4f, 0xf0, 0x44, 0xb9, 0x7e, 0x30, 0xf0, 0xf4, 0x30, 0x3c, 0xb6, 0x1d, 0x31,
-	0x6a, 0x33, 0x69, 0xd4, 0xbf, 0x33, 0x8b, 0x0f, 0x1d, 0xb7, 0x3d, 0xde, 0x6b, 0x07, 0x27, 0x83,
-	0x48, 0x53, 0xb5, 0x59, 0x10, 0xf8, 0x9e, 0x63, 0x74, 0xdb, 0xe3, 0x1d, 0xe6, 0x07, 0x43, 0xb6,
-	0xd3, 0x1e, 0x20, 0x47, 0xc9, 0x34, 0xba, 0x89, 0xb5, 0x2f, 0xfe, 0xc5, 0x5a, 0xf1, 0x24, 0xc2,
-	0x73, 0x9d, 0xb6, 0xe3, 0x33, 0x6f, 0x94, 0xc4, 0xd3, 0xac, 0xc1, 0xca, 0xb3, 0x84, 0xfd, 0x2a,
-	0x44, 0x39, 0x69, 0xfe, 0xbc, 0x02, 0x95, 0x14, 0x21, 0x37, 0xa0, 0x1c, 0x4a, 0xdf, 0x2a, 0x35,
-	0x4a, 0xad, 0x6a, 0x67, 0x69, 0x7a, 0xba, 0x5d, 0x3e, 0xa2, 0x07, 0x34, 0xc2, 0xc8, 0x1d, 0xa8,
-	0xba, 0xf8, 0xba, 0x2b, 0xf8, 0xb7, 0xde, 0xc0, 0xba, 0xd4, 0x28, 0xb5, 0x96, 0x77, 0x89, 0x9d,
-	0x64, 0xc6, 0xee, 0xa5, 0x0c, 0x3d, 0x13, 0x22, 0x5d, 0x80, 0xc8, 0x7f, 0xa2, 0x52, 0x36, 0x2a,
-	0x57, 0x33, 0x95, 0xa7, 0xfd, 0x5e, 0x37, 0xa6, 0x3a, 0xab, 0xd3, 0xd3, 0x6d, 0x38, 0xdb, 0xd3,
-	0x9c, 0x1a, 0x69, 0xc0, 0x32, 0x0b, 0x82, 0x03, 0x76, 0x8c, 0xfe, 0x23, 0x9c, 0x58, 0x0b, 0x51,
-	0x64, 0x34, 0x0f, 0x91, 0x17, 0xb0, 0x2e, 0x51, 0x89, 0x50, 0x3a, 0xf8, 0x74, 0x8c, 0x52, 0x7a,
-	0x2e, 0x2a, 0xeb, 0x72, 0xa3, 0xdc, 0x5a, 0xde, 0x6d, 0x65, 0xde, 0xd2, 0x13, 0xda, 0xb4, 0x28,
-	0x7a, 0x9f, 0x6b, 0x39, 0xa1, 0xb3, 0x26, 0x88, 0x0d, 0x44, 0x69, 0xa6, 0x43, 0xd5, 0x61, 0xee,
-	0x00, 0xef, 0x73, 0x76, 0xec, 0xa3, 0x6b, 0x2d, 0x36, 0x4a, 0xad, 0x0a, 0x9d, 0xc3, 0x90, 0x87,
-	0x50, 0x8b, 0x2b, 0x61, 0x9f, 0x33, 0x7f, 0xa2, 0x3d, 0x47, 0x59, 0x4b, 0xe6, 0xcc, 0x5b, 0x59,
-	0x14, 0x0f, 0xce, 0xf3, 0xc9, 0x71, 0x8b, 0x6a, 0xe4, 0x0d, 0xac, 0x9d, 0x84, 0x4a, 0x8b, 0x91,
-	0xf7, 0x06, 0x9f, 0x06, 0xa6, 0x9a, 0xac, 0x8a, 0x31, 0xf5, 0xc4, 0x3e, 0x2b, 0x00, 0x3b, 0x2d,
-	0x00, 0xb3, 0x78, 0xe9, 0xb8, 0xf6, 0x78, 0xcf, 0x0e, 0x4e, 0x06, 0x76, 0x54, 0x4e, 0x76, 0xae,
-	0x9c, 0xec, 0xb4, 0x9c, 0xec, 0x47, 0x05, 0xab, 0x74, 0xc6, 0x0f, 0xf9, 0x3f, 0x2c, 0x0c, 0xd1,
-	0x0f, 0xac, 0xaa, 0xf1, 0xb7, 0x92, 0x85, 0xfe, 0x10, 0xfd, 0x80, 0x1a, 0x8a, 0xbc, 0x07, 0x4b,
-	0x81, 0x1f, 0x0e, 0x3c, 0xae, 0x2c, 0x30, 0x69, 0xae, 0x65, 0x52, 0x87, 0x06, 0xa7, 0x29, 0x1f,
-	0xe5, 0x30, 0x54, 0x28, 0x0f, 0x44, 0xb4, 0xeb, 0x79, 0x2a, 0xce, 0xe1, 0x72, 0x9c, 0xc3, 0x59,
-	0x86, 0xfc, 0x50, 0x82, 0xeb, 0x8e, 0xc9, 0xca, 0x63, 0xc6, 0xd9, 0x00, 0x47, 0xc8, 0xf5, 0x61,
-	0xe2, 0xeb, 0x8a, 0xf1, 0xf5, 0xfc, 0xdd, 0x32, 0xd0, 0x9d, 0x6b, 0x9c, 0x5e, 0xe4, 0x94, 0x7c,
-	0x00, 0xeb, 0x59, 0x8a, 0x5e, 0xa0, 0x54, 0xe6, 0x2e, 0x56, 0x1a, 0xe5, 0x56, 0x95, 0xce, 0x12,
-	0xa4, 0x0e, 0x95, 0xd0, 0xeb, 0x2a, 0x75, 0x44, 0x0f, 0xac, 0x55, 0x53, 0xa9, 0xd9, 0x9e, 0xb4,
-	0xa0, 0x16, 0x7a, 0x1d, 0xc6, 0x39, 0xca, 0xae, 0xe0, 0x1a, 0xb9, 0xb6, 0x6a, 0x46, 0xa4, 0x08,
-	0x47, 0x25, 0x9f, 0x42, 0x91, 0xa1, 0xb5, 0xb8, 0xe4, 0x73, 0x50, 0x64, 0x2b, 0x60, 0x4a, 0xbd,
-	0x12, 0xd2, 0x3d, 0x64, 0x5a, 0xa3, 0xe4, 0xd6, 0x7a, 0x6c, 0xab, 0x00, 0x93, 0xdb, 0xb0, 0xaa,
-	0x25, 0x73, 0x4e, 0x3c, 0x3e, 0x78, 0x8c, 0x7a, 0x28, 0x5c, 0x8b, 0x18, 0xc1, 0x02, 0x1a, 0x9d,
-	0x33, 0x75, 0x70, 0x88, 0x72, 0xc4, 0x78, 0x14, 0xdf, 0x55, 0x73, 0x4f, 0xb3, 0x04, 0x79, 0x1f,
-	0xd6, 0x32, 0x50, 0x28, 0x2f, 0x4a, 0xb1, 0xb5, 0x61, 0xec, 0xce, 0xe0, 0x85, 0x36, 0xa2, 0x42,
-	0xe8, 0x23, 0xe9, 0x5b, 0xd7, 0x8c, 0xf4, 0x1c, 0x26, 0x3a, 0x3d, 0xbe, 0x46, 0x27, 0xed, 0xb7,
-	0x4d, 0x13, 0x43, 0x1e, 0x22, 0x77, 0xe0, 0xaa, 0x23, 0xb8, 0x96, 0xc2, 0xf7, 0x51, 0x3e, 0x61,
-	0x23, 0x54, 0x01, 0x73, 0xd0, 0xba, 0x6e, 0x4c, 0xce, 0xa3, 0xc8, 0x67, 0x70, 0x83, 0x05, 0x81,
-	0xea, 0xf3, 0x7d, 0x3e, 0xc9, 0xd0, 0xd4, 0x83, 0x65, 0x3c, 0x5c, 0x2c, 0x40, 0x76, 0x61, 0xc3,
-	0x1b, 0x05, 0x28, 0x95, 0xe0, 0xa6, 0x9a, 0x52, 0xc5, 0x1b, 0x46, 0x71, 0x2e, 0x17, 0xe5, 0xdd,
-	0xe3, 0x4a, 0x33, 0xdf, 0x37, 0x70, 0xbf, 0x67, 0xd5, 0xe3, 0xbc, 0x9f, 0x47, 0xc9, 0x5d, 0x58,
-	0x65, 0xae, 0x6b, 0x32, 0xc5, 0xfc, 0x23, 0xe9, 0x2b, 0xeb, 0x7f, 0x51, 0x71, 0x75, 0xc8, 0xf4,
-	0x74, 0x7b, 0x75, 0xff, 0x8c, 0xa1, 0x07, 0x8a, 0x16, 0x24, 0xa3, 0x2a, 0x18, 0x4e, 0x5c, 0xc9,
-	0xb4, 0x90, 0x69, 0x48, 0x37, 0x4d, 0x48, 0x45, 0x98, 0x7c, 0x0c, 0x9b, 0x6a, 0xc2, 0x9d, 0xaf,
-	0x3d, 0x3d, 0xa4, 0x18, 0xf8, 0xcc, 0xc1, 0x7d, 0xdf, 0x17, 0xaf, 0xd0, 0xb5, 0x6e, 0x19, 0x85,
-	0x0b, 0xd8, 0xfa, 0x4f, 0x25, 0xd8, 0x9c, 0xff, 0x60, 0x92, 0x35, 0x28, 0x9f, 0xe0, 0x24, 0xfe,
-	0x29, 0x68, 0xb4, 0x24, 0x2e, 0x5c, 0x1e, 0x33, 0x3f, 0xc4, 0xe4, 0x73, 0x78, 0xc7, 0xa7, 0xaa,
-	0xe8, 0x96, 0xc6, 0xc6, 0xef, 0x5e, 0xfa, 0xb4, 0xd4, 0x7c, 0x09, 0xd7, 0xe6, 0xbe, 0xa4, 0x64,
-	0x0b, 0x20, 0xad, 0xeb, 0x7e, 0x2f, 0x89, 0x2d, 0x87, 0x44, 0xb7, 0xc2, 0xb8, 0xe0, 0x93, 0xa8,
-	0x69, 0x8f, 0x14, 0x4a, 0x65, 0x62, 0xad, 0xd0, 0x02, 0xda, 0xec, 0xc1, 0xf5, 0xf4, 0xc3, 0x48,
-	0x1e, 0x02, 0x8a, 0x2a, 0x10, 0x5c, 0x61, 0xfe, 0xf1, 0x2b, 0xbd, 0xfd, 0xf1, 0x6b, 0xfe, 0x52,
-	0x82, 0x85, 0xe8, 0xd9, 0x24, 0x16, 0x2c, 0x39, 0x43, 0x66, 0xea, 0x3e, 0x8e, 0x29, 0xdd, 0x46,
-	0x0f, 0x46, 0xb4, 0x7c, 0x8e, 0xaf, 0xb5, 0x09, 0xa5, 0x4a, 0xb3, 0x3d, 0xb9, 0x07, 0x70, 0xec,
-	0x71, 0x26, 0x27, 0xa6, 0x2c, 0xca, 0xc6, 0xd9, 0xad, 0x73, 0xef, 0xb1, 0xdd, 0xc9, 0xf8, 0xf8,
-	0x17, 0xcb, 0x29, 0xd4, 0xef, 0x41, 0xad, 0x40, 0xcf, 0xb9, 0xb3, 0x8d, 0xfc, 0x9d, 0x55, 0xf3,
-	0x39, 0xbe, 0x09, 0x8b, 0xf1, 0x79, 0x08, 0x81, 0x05, 0xce, 0x46, 0x98, 0xa8, 0x99, 0x75, 0xf3,
-	0x73, 0xa8, 0x66, 0x5f, 0x3e, 0xd9, 0x05, 0x70, 0x04, 0xe7, 0xe8, 0x68, 0x21, 0xd3, 0xac, 0x9c,
-	0x8d, 0x06, 0xdd, 0x94, 0xa2, 0x39, 0xa9, 0xe6, 0x1e, 0x54, 0x33, 0x62, 0x9e, 0x87, 0x08, 0xd3,
-	0x93, 0x20, 0x0d, 0xcc, 0xac, 0x9b, 0xbf, 0x96, 0x21, 0x37, 0x26, 0xcc, 0x55, 0xdb, 0x84, 0x45,
-	0x4f, 0xa9, 0x10, 0x65, 0xa2, 0x98, 0xec, 0x48, 0x0b, 0x2a, 0x8e, 0xef, 0x21, 0xd7, 0xfd, 0x9e,
-	0x99, 0x44, 0xaa, 0x9d, 0x2b, 0xd3, 0xd3, 0xed, 0x4a, 0x37, 0xc1, 0x68, 0xc6, 0x92, 0x1d, 0x58,
-	0x76, 0x7c, 0x2f, 0x25, 0xe2, 0x81, 0xa3, 0x53, 0x9b, 0x9e, 0x6e, 0x2f, 0x77, 0x0f, 0xfa, 0x99,
-	0x7c, 0x5e, 0x26, 0x72, 0xaa, 0x1c, 0x11, 0x24, 0x63, 0x47, 0x95, 0x26, 0x3b, 0xf2, 0x12, 0x56,
-	0x3c, 0xf7, 0xb9, 0x38, 0x41, 0xde, 0x35, 0x23, 0x98, 0xb5, 0x68, 0x72, 0x73, 0x7b, 0xce, 0x0c,
-	0x64, 0xf7, 0xf3, 0x82, 0xe6, 0xba, 0x3a, 0xeb, 0xd3, 0xd3, 0xed, 0x95, 0x7e, 0x2f, 0x87, 0xd3,
-	0xf3, 0xf6, 0xc8, 0x5d, 0xb0, 0xd0, 0xb4, 0xf8, 0xe1, 0xa3, 0xee, 0xfd, 0xfd, 0x50, 0x0f, 0x91,
-	0xeb, 0xa4, 0x93, 0xcc, 0xec, 0x51, 0xa1, 0x17, 0xf2, 0xf5, 0x09, 0x90, 0x59, 0x9f, 0x73, 0x4a,
-	0xe4, 0xf1, 0xf9, 0xb6, 0xfe, 0xe4, 0xad, 0x6d, 0x1d, 0xcf, 0x9f, 0x76, 0x36, 0x40, 0x47, 0x83,
-	0x9c, 0x6d, 0xec, 0xe7, 0x6a, 0x6b, 0xf7, 0xb7, 0x12, 0xd4, 0xd2, 0xfe, 0x7a, 0x86, 0x72, 0xec,
-	0x39, 0x48, 0xbe, 0x84, 0xf2, 0x03, 0xd4, 0x64, 0x73, 0x66, 0x62, 0x33, 0x53, 0x6a, 0x7d, 0x7d,
-	0x06, 0x6f, 0x5a, 0xdf, 0xff, 0xf9, 0xf7, 0x8f, 0x97, 0x08, 0x59, 0x33, 0x93, 0xf7, 0x78, 0x27,
-	0x9b, 0x7a, 0xc9, 0x10, 0xe0, 0x01, 0x66, 0x5f, 0xf8, 0x45, 0x26, 0x1b, 0x33, 0x78, 0xa1, 0xd7,
-	0x9b, 0x0d, 0xe3, 0xa1, 0x4e, 0xac, 0xa2, 0x87, 0x76, 0xd2, 0xe2, 0x9d, 0xee, 0xef, 0xd3, 0xad,
-	0xd2, 0x1f, 0xd3, 0xad, 0xd2, 0x5f, 0xd3, 0xad, 0xd2, 0x37, 0x1f, 0xfd, 0xb7, 0x59, 0x3f, 0x2e,
-	0xb5, 0xcc, 0xd8, 0xf1, 0xa2, 0x99, 0xcc, 0xf7, 0xfe, 0x09, 0x00, 0x00, 0xff, 0xff, 0x0b, 0x1a,
-	0xe6, 0x75, 0x88, 0x0c, 0x00, 0x00,
+	// 1337 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0xa4, 0x57, 0x4f, 0x6f, 0x1b, 0x45,
+	0x14, 0x97, 0xeb, 0x34, 0xb1, 0x5f, 0x9a, 0x38, 0x99, 0xa6, 0xe9, 0xd6, 0xb4, 0x89, 0xf1, 0xa1,
+	0x32, 0x08, 0xd6, 0x4d, 0x22, 0xfe, 0xa8, 0xa2, 0x82, 0xd8, 0xae, 0x5a, 0x53, 0xb7, 0x0d, 0xdb,
+	0xa4, 0x48, 0x5c, 0xaa, 0xc9, 0xee, 0xeb, 0x7a, 0xc9, 0x7a, 0x66, 0x35, 0x33, 0xeb, 0xd6, 0x3d,
+	0xf2, 0x01, 0xb8, 0xc0, 0xa7, 0xe1, 0x8e, 0xe0, 0x88, 0xc4, 0x85, 0x53, 0x84, 0x2c, 0x3e, 0x08,
+	0xda, 0xd9, 0x3f, 0xd9, 0xac, 0x9d, 0x82, 0xd4, 0xdb, 0xcc, 0xef, 0xf7, 0xfe, 0xcd, 0x9b, 0xf7,
+	0x66, 0xdf, 0xc2, 0x96, 0x44, 0x31, 0x46, 0xd1, 0x96, 0xa8, 0x94, 0xc7, 0x5c, 0x99, 0x2d, 0xcc,
+	0x40, 0x70, 0xc5, 0xc9, 0x92, 0xed, 0x87, 0x52, 0xa1, 0xa8, 0x6f, 0xb8, 0xdc, 0xe5, 0x1a, 0x6b,
+	0x47, 0xab, 0x98, 0xae, 0xdf, 0x74, 0x39, 0x77, 0x7d, 0x6c, 0xd3, 0xc0, 0x6b, 0x53, 0xc6, 0xb8,
+	0xa2, 0xca, 0xe3, 0x2c, 0x51, 0xae, 0x0f, 0x5c, 0x4f, 0x0d, 0xc3, 0x63, 0xd3, 0xe6, 0xa3, 0x36,
+	0x15, 0x5a, 0xfd, 0x7b, 0xbd, 0xf8, 0xd8, 0x76, 0xda, 0xe3, 0xbd, 0x76, 0x70, 0xe2, 0x46, 0x9a,
+	0xb2, 0x4d, 0x83, 0xc0, 0xf7, 0x6c, 0xad, 0xdb, 0x1e, 0xef, 0x50, 0x3f, 0x18, 0xd2, 0x9d, 0xb6,
+	0x8b, 0x0c, 0x05, 0x55, 0xe8, 0x24, 0xd6, 0xbe, 0xfa, 0x0f, 0x6b, 0xc5, 0x93, 0x70, 0xcf, 0xb1,
+	0xdb, 0xb6, 0x4f, 0xbd, 0x51, 0x12, 0x4f, 0xb3, 0x06, 0x2b, 0xcf, 0x12, 0xf6, 0x9b, 0x10, 0xc5,
+	0xa4, 0xf9, 0xd7, 0x0a, 0x54, 0x52, 0x84, 0xdc, 0x80, 0x72, 0x28, 0x7c, 0xa3, 0xd4, 0x28, 0xb5,
+	0xaa, 0x9d, 0xa5, 0xe9, 0xe9, 0x76, 0xf9, 0xc8, 0x1a, 0x58, 0x11, 0x46, 0xee, 0x40, 0xd5, 0xc1,
+	0xd7, 0x5d, 0xce, 0x5e, 0x7a, 0xae, 0x71, 0xa9, 0x51, 0x6a, 0x2d, 0xef, 0x12, 0x33, 0xc9, 0x8c,
+	0xd9, 0x4b, 0x19, 0xeb, 0x4c, 0x88, 0x74, 0x01, 0x22, 0xff, 0x89, 0x4a, 0x59, 0xab, 0x5c, 0xcd,
+	0x54, 0x9e, 0xf6, 0x7b, 0xdd, 0x98, 0xea, 0xac, 0x4e, 0x4f, 0xb7, 0xe1, 0x6c, 0x6f, 0xe5, 0xd4,
+	0x48, 0x03, 0x96, 0x69, 0x10, 0x0c, 0xe8, 0x31, 0xfa, 0x8f, 0x70, 0x62, 0x2c, 0x44, 0x91, 0x59,
+	0x79, 0x88, 0x3c, 0x87, 0x75, 0x81, 0x92, 0x87, 0xc2, 0xc6, 0xa7, 0x63, 0x14, 0xc2, 0x73, 0x50,
+	0x1a, 0x97, 0x1b, 0xe5, 0xd6, 0xf2, 0x6e, 0x2b, 0xf3, 0x96, 0x9e, 0xd0, 0xb4, 0x8a, 0xa2, 0xf7,
+	0x99, 0x12, 0x13, 0x6b, 0xd6, 0x04, 0x31, 0x81, 0x48, 0x45, 0x55, 0x28, 0x3b, 0xd4, 0x71, 0xf1,
+	0x3e, 0xa3, 0xc7, 0x3e, 0x3a, 0xc6, 0x62, 0xa3, 0xd4, 0xaa, 0x58, 0x73, 0x18, 0xf2, 0x10, 0x6a,
+	0x71, 0x25, 0xec, 0x33, 0xea, 0x4f, 0x94, 0x67, 0x4b, 0x63, 0x49, 0x9f, 0x79, 0x2b, 0x8b, 0xe2,
+	0xc1, 0x79, 0x3e, 0x39, 0x6e, 0x51, 0x8d, 0xbc, 0x81, 0xb5, 0x93, 0x50, 0x2a, 0x3e, 0xf2, 0xde,
+	0xe0, 0xd3, 0x40, 0x57, 0x93, 0x51, 0xd1, 0xa6, 0x9e, 0x98, 0x67, 0x05, 0x60, 0xa6, 0x05, 0xa0,
+	0x17, 0x2f, 0x6c, 0xc7, 0x1c, 0xef, 0x99, 0xc1, 0x89, 0x6b, 0x46, 0xe5, 0x64, 0xe6, 0xca, 0xc9,
+	0x4c, 0xcb, 0xc9, 0x7c, 0x54, 0xb0, 0x6a, 0xcd, 0xf8, 0x21, 0xef, 0xc3, 0xc2, 0x10, 0xfd, 0xc0,
+	0xa8, 0x6a, 0x7f, 0x2b, 0x59, 0xe8, 0x0f, 0xd1, 0x0f, 0x2c, 0x4d, 0x91, 0x0f, 0x60, 0x29, 0xf0,
+	0x43, 0xd7, 0x63, 0xd2, 0x00, 0x9d, 0xe6, 0x5a, 0x26, 0x75, 0xa0, 0x71, 0x2b, 0xe5, 0xa3, 0x1c,
+	0x86, 0x12, 0xc5, 0x80, 0x47, 0xbb, 0x9e, 0x27, 0xe3, 0x1c, 0x2e, 0xc7, 0x39, 0x9c, 0x65, 0xc8,
+	0x8f, 0x25, 0xb8, 0x6e, 0xeb, 0xac, 0x3c, 0xa6, 0x8c, 0xba, 0x38, 0x42, 0xa6, 0x0e, 0x12, 0x5f,
+	0x57, 0xb4, 0xaf, 0xc3, 0x77, 0xcb, 0x40, 0x77, 0xae, 0x71, 0xeb, 0x22, 0xa7, 0xe4, 0x23, 0x58,
+	0xcf, 0x52, 0xf4, 0x1c, 0x85, 0xd4, 0x77, 0xb1, 0xd2, 0x28, 0xb7, 0xaa, 0xd6, 0x2c, 0x41, 0xea,
+	0x50, 0x09, 0xbd, 0xae, 0x94, 0x47, 0xd6, 0xc0, 0x58, 0xd5, 0x95, 0x9a, 0xed, 0x49, 0x0b, 0x6a,
+	0xa1, 0xd7, 0xa1, 0x8c, 0xa1, 0xe8, 0x72, 0xa6, 0x90, 0x29, 0xa3, 0xa6, 0x45, 0x8a, 0x70, 0x54,
+	0xf2, 0x29, 0x14, 0x19, 0x5a, 0x8b, 0x4b, 0x3e, 0x07, 0x45, 0xb6, 0x02, 0x2a, 0xe5, 0x2b, 0x2e,
+	0x9c, 0x03, 0xaa, 0x14, 0x0a, 0x66, 0xac, 0xc7, 0xb6, 0x0a, 0x30, 0xb9, 0x0d, 0xab, 0x4a, 0x50,
+	0xfb, 0xc4, 0x63, 0xee, 0x63, 0x54, 0x43, 0xee, 0x18, 0x44, 0x0b, 0x16, 0xd0, 0xe8, 0x9c, 0xa9,
+	0x83, 0x03, 0x14, 0x23, 0xca, 0xa2, 0xf8, 0xae, 0xea, 0x7b, 0x9a, 0x25, 0xc8, 0x87, 0xb0, 0x96,
+	0x81, 0x5c, 0x7a, 0x51, 0x8a, 0x8d, 0x0d, 0x6d, 0x77, 0x06, 0x2f, 0xb4, 0x91, 0xc5, 0xb9, 0x3a,
+	0x12, 0xbe, 0x71, 0x4d, 0x4b, 0xcf, 0x61, 0xa2, 0xd3, 0xe3, 0x6b, 0xb4, 0xd3, 0x7e, 0xdb, 0xd4,
+	0x31, 0xe4, 0xa1, 0xe8, 0x4c, 0xa1, 0xd7, 0xc3, 0x97, 0x34, 0xf4, 0xd5, 0xe1, 0x10, 0x47, 0x68,
+	0x6c, 0xc5, 0x67, 0x3a, 0x8f, 0x92, 0x3b, 0x70, 0xd5, 0xe6, 0x4c, 0x09, 0xee, 0xfb, 0x28, 0x9e,
+	0xd0, 0x11, 0xca, 0x80, 0xda, 0x68, 0x5c, 0xd7, 0xc2, 0xf3, 0x28, 0xf2, 0x05, 0xdc, 0xa0, 0x41,
+	0x20, 0xfb, 0x6c, 0x9f, 0x4d, 0x32, 0x34, 0x8d, 0xc4, 0xd0, 0x91, 0x5c, 0x2c, 0x40, 0x76, 0x61,
+	0xc3, 0x1b, 0x05, 0x28, 0x24, 0x67, 0xba, 0xea, 0x52, 0xc5, 0x1b, 0x5a, 0x71, 0x2e, 0x17, 0x9d,
+	0xc5, 0x63, 0x52, 0x51, 0xdf, 0xd7, 0x70, 0xbf, 0x67, 0xd4, 0xe3, 0xb3, 0x9c, 0x47, 0xc9, 0x5d,
+	0x58, 0xa5, 0x8e, 0xa3, 0x33, 0x4a, 0xfd, 0x23, 0xe1, 0x4b, 0xe3, 0xbd, 0xa8, 0x08, 0x3b, 0x64,
+	0x7a, 0xba, 0xbd, 0xba, 0x7f, 0xc6, 0x58, 0x03, 0x69, 0x15, 0x24, 0xa3, 0x6a, 0x19, 0x4e, 0x1c,
+	0x41, 0x15, 0x17, 0x69, 0x48, 0x37, 0x75, 0x48, 0x45, 0x98, 0x7c, 0x0a, 0x9b, 0x72, 0xc2, 0xec,
+	0x6f, 0x3d, 0x35, 0xb4, 0x30, 0xf0, 0xa9, 0x8d, 0xfb, 0xbe, 0xcf, 0x5f, 0xa1, 0x63, 0xdc, 0xd2,
+	0x0a, 0x17, 0xb0, 0xf5, 0x9f, 0x4b, 0xb0, 0x39, 0xff, 0x61, 0x25, 0x6b, 0x50, 0x3e, 0xc1, 0x49,
+	0xfc, 0x45, 0xb1, 0xa2, 0x25, 0x71, 0xe0, 0xf2, 0x98, 0xfa, 0x21, 0x26, 0x1f, 0x91, 0x77, 0x7c,
+	0xd2, 0x8a, 0x6e, 0xad, 0xd8, 0xf8, 0xdd, 0x4b, 0x9f, 0x97, 0x9a, 0x2f, 0xe0, 0xda, 0xdc, 0x17,
+	0x97, 0x6c, 0x01, 0xa4, 0xf5, 0xdf, 0xef, 0x25, 0xb1, 0xe5, 0x90, 0xe8, 0x56, 0x28, 0xe3, 0x6c,
+	0x12, 0x35, 0xf7, 0x91, 0x44, 0x21, 0x75, 0xac, 0x15, 0xab, 0x80, 0x36, 0x7b, 0x70, 0x3d, 0xfd,
+	0xb0, 0x24, 0x0f, 0x86, 0x85, 0x32, 0xe0, 0x4c, 0x62, 0xfe, 0x91, 0x2c, 0xbd, 0xfd, 0x91, 0x6c,
+	0xfe, 0x52, 0x82, 0x85, 0xe8, 0x79, 0x25, 0x06, 0x2c, 0xd9, 0x43, 0xaa, 0xfb, 0x23, 0x8e, 0x29,
+	0xdd, 0x46, 0x0f, 0x4b, 0xb4, 0x3c, 0xc4, 0xd7, 0x4a, 0x87, 0x52, 0xb5, 0xb2, 0x3d, 0xb9, 0x07,
+	0x70, 0xec, 0x31, 0x2a, 0x26, 0xba, 0x2c, 0xca, 0xda, 0xd9, 0xad, 0x73, 0xef, 0xb6, 0xd9, 0xc9,
+	0xf8, 0xf8, 0x6b, 0x97, 0x53, 0xa8, 0xdf, 0x83, 0x5a, 0x81, 0x9e, 0x73, 0x67, 0x1b, 0xf9, 0x3b,
+	0xab, 0xe6, 0x73, 0x7c, 0x13, 0x16, 0xe3, 0xf3, 0x10, 0x02, 0x0b, 0x8c, 0x8e, 0x30, 0x51, 0xd3,
+	0xeb, 0xe6, 0x97, 0x50, 0xcd, 0x46, 0x03, 0xb2, 0x0b, 0x60, 0x73, 0xc6, 0xd0, 0x56, 0x5c, 0xa4,
+	0x59, 0x39, 0x1b, 0x21, 0xba, 0x29, 0x65, 0xe5, 0xa4, 0x9a, 0x7b, 0x50, 0xcd, 0x88, 0x79, 0x1e,
+	0x22, 0x4c, 0x4d, 0x82, 0x34, 0x30, 0xbd, 0x6e, 0xfe, 0x5a, 0x86, 0xdc, 0x38, 0x31, 0x57, 0x6d,
+	0x13, 0x16, 0x3d, 0x29, 0x43, 0x14, 0x89, 0x62, 0xb2, 0x23, 0x2d, 0xa8, 0xd8, 0xbe, 0x87, 0x4c,
+	0xf5, 0x7b, 0x7a, 0x62, 0xa9, 0x76, 0xae, 0x4c, 0x4f, 0xb7, 0x2b, 0xdd, 0x04, 0xb3, 0x32, 0x96,
+	0xec, 0xc0, 0xb2, 0xed, 0x7b, 0x29, 0x11, 0x0f, 0x26, 0x9d, 0xda, 0xf4, 0x74, 0x7b, 0xb9, 0x3b,
+	0xe8, 0x67, 0xf2, 0x79, 0x99, 0xc8, 0xa9, 0xb4, 0x79, 0x90, 0x8c, 0x27, 0x55, 0x2b, 0xd9, 0x91,
+	0x17, 0xb0, 0xe2, 0x39, 0x87, 0xfc, 0x04, 0x59, 0x57, 0x8f, 0x6a, 0xc6, 0xa2, 0xce, 0xcd, 0xed,
+	0x39, 0xb3, 0x92, 0xd9, 0xcf, 0x0b, 0xea, 0xeb, 0xea, 0xac, 0x4f, 0x4f, 0xb7, 0x57, 0xfa, 0xbd,
+	0x1c, 0x6e, 0x9d, 0xb7, 0x47, 0xee, 0x82, 0x81, 0xba, 0xc5, 0x0f, 0x1e, 0x75, 0xef, 0xef, 0x87,
+	0x6a, 0x88, 0x4c, 0x25, 0x9d, 0xa4, 0x67, 0x94, 0x8a, 0x75, 0x21, 0x5f, 0x9f, 0x00, 0x99, 0xf5,
+	0x39, 0xa7, 0x44, 0x1e, 0x9f, 0x6f, 0xeb, 0xcf, 0xde, 0xda, 0xd6, 0xf1, 0x9c, 0x6a, 0x66, 0x83,
+	0x76, 0x34, 0xf0, 0x99, 0xda, 0x7e, 0xae, 0xb6, 0x76, 0x7f, 0x2b, 0x41, 0x2d, 0xed, 0xaf, 0x67,
+	0x28, 0xc6, 0x9e, 0x8d, 0xe4, 0x6b, 0x28, 0x3f, 0x40, 0x45, 0x36, 0x67, 0x26, 0x3b, 0x3d, 0xcd,
+	0xd6, 0xd7, 0x67, 0xf0, 0xa6, 0xf1, 0xc3, 0x9f, 0xff, 0xfc, 0x74, 0x89, 0x90, 0x35, 0x3d, 0xa1,
+	0x8f, 0x77, 0xb2, 0xe9, 0x98, 0x0c, 0x01, 0x1e, 0x60, 0xf6, 0xa9, 0xbf, 0xc8, 0x64, 0x63, 0x06,
+	0x2f, 0xf4, 0x7a, 0xb3, 0xa1, 0x3d, 0xd4, 0x89, 0x51, 0xf4, 0xd0, 0x4e, 0x5a, 0xbc, 0xd3, 0xfd,
+	0x7d, 0xba, 0x55, 0xfa, 0x63, 0xba, 0x55, 0xfa, 0x7b, 0xba, 0x55, 0xfa, 0xee, 0x93, 0xff, 0xf7,
+	0x4f, 0x10, 0x97, 0x5a, 0x66, 0xec, 0x78, 0x51, 0x4f, 0xf0, 0x7b, 0xff, 0x06, 0x00, 0x00, 0xff,
+	0xff, 0xcc, 0xd4, 0xb7, 0x19, 0xb0, 0x0c, 0x00, 0x00,
 }
 
 // Reference imports to suppress errors if they are not otherwise used.
@@ -1037,6 +1046,15 @@ func (m *Settings) MarshalToSizedBuffer(dAtA []byte) (int, error) {
 		i -= len(m.XXX_unrecognized)
 		copy(dAtA[i:], m.XXX_unrecognized)
 	}
+	if len(m.UiDefaultTheme) > 0 {
+		i -= len(m.UiDefaultTheme)
+		copy(dAtA[i:], m.UiDefaultTheme)
+		i = encodeVarintSettings(dAtA, i, uint64(len(m.UiDefaultTheme)))
+		i--
+		dAtA[i] = 0x1
+		i--
+		dAtA[i] = 0xf2
+	}
 	if m.SyncWithReplaceAllowed {
 		i--
 		if m.SyncWithReplaceAllowed {
@@ -1872,6 +1890,10 @@ func (m *Settings) Size() (n int) {
 	if m.SyncWithReplaceAllowed {
 		n += 3
 	}
+	l = len(m.UiDefaultTheme)
+	if l > 0 {
+		n += 2 + l + sovSettings(uint64(l))
+	}
 	if m.XXX_unrecognized != nil {
 		n += len(m.XXX_unrecognized)
 	}
@@ -3086,6 +3108,38 @@ func (m *Settings) Unmarshal(dAtA []byte) error {
 				}
 			}
 			m.SyncWithReplaceAllowed = bool(v != 0)
+		case 30:
+			if wireType != 2 {
+				return fmt.Errorf("proto: wrong wireType = %d for field UiDefaultTheme", wireType)
+			}
+			var stringLen uint64
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowSettings
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := dAtA[iNdEx]
+				iNdEx++
+				stringLen |= uint64(b&0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+			intStringLen := int(stringLen)
+			if intStringLen < 0 {
+				return ErrInvalidLengthSettings
+			}
+			postIndex := iNdEx + intStringLen
+			if postIndex < 0 {
+				return ErrInvalidLengthSettings
+			}
+			if postIndex > l {
+				return io.ErrUnexpectedEOF
+			}
+			m.UiDefaultTheme = string(dAtA[iNdEx:postIndex])
+			iNdEx = postIndex
 		default:
 			iNdEx = preIndex
 			skippy, err := skipSettings(dAtA[iNdEx:])
diff --git a/server/settings/settings.go b/server/settings/settings.go
index db11a548f056d..4730112585b44 100644
--- a/server/settings/settings.go
+++ b/server/settings/settings.go
@@ -116,6 +116,7 @@ func (s *Server) Get(ctx context.Context, _ *settingspkg.SettingsQuery) (*settin
 		UserLoginsDisabled:        userLoginsDisabled,
 		KustomizeVersions:         kustomizeVersions,
 		UiCssURL:                  argoCDSettings.UiCssURL,
+		UiDefaultTheme:            argoCDSettings.UiDefaultTheme,
 		TrackingMethod:            trackingMethod,
 		InstallationID:            installationID,
 		ExecEnabled:               argoCDSettings.ExecEnabled,
diff --git a/server/settings/settings.proto b/server/settings/settings.proto
index 05ec4dab178fc..c5e03a26faf47 100644
--- a/server/settings/settings.proto
+++ b/server/settings/settings.proto
@@ -40,6 +40,7 @@ message Settings {
     string uiBannerPosition = 20;
     string statusBadgeRootUrl = 21;
     bool execEnabled = 22;
+    string uiDefaultTheme = 30;
     string controllerNamespace = 23;
     bool appsInAnyNamespaceEnabled = 24;
     bool impersonationEnabled = 25;
diff --git a/server/settings/settings_test.go b/server/settings/settings_test.go
index aba42865d4c7f..0f910bb554e69 100644
--- a/server/settings/settings_test.go
+++ b/server/settings/settings_test.go
@@ -114,4 +114,29 @@ func TestSettingsServer(t *testing.T) {
 		assert.NotNil(t, resp.ResourceOverrides)
 		assert.NotEmpty(t, resp.ResourceOverrides["*/*"])
 	})
+
+	t.Run("TestGetUiDefaultTheme", func(t *testing.T) {
+		settingsServer := newServer(map[string]string{
+			"ui.defaulttheme": "dark",
+		})
+		resp, err := settingsServer.Get(t.Context(), nil)
+		require.NoError(t, err)
+		assert.Equal(t, "dark", resp.UiDefaultTheme)
+	})
+
+	t.Run("TestGetUiDefaultThemeAuto", func(t *testing.T) {
+		settingsServer := newServer(map[string]string{
+			"ui.defaulttheme": "auto",
+		})
+		resp, err := settingsServer.Get(t.Context(), nil)
+		require.NoError(t, err)
+		assert.Equal(t, "auto", resp.UiDefaultTheme)
+	})
+
+	t.Run("TestGetUiDefaultThemeNotSet", func(t *testing.T) {
+		settingsServer := newServer(map[string]string{})
+		resp, err := settingsServer.Get(t.Context(), nil)
+		require.NoError(t, err)
+		assert.Empty(t, resp.UiDefaultTheme)
+	})
 }
diff --git a/ui/src/app/app.tsx b/ui/src/app/app.tsx
index 54434bc15e498..c4a7d9e469aca 100644
--- a/ui/src/app/app.tsx
+++ b/ui/src/app/app.tsx
@@ -122,6 +122,9 @@ export class App extends React.Component<{}, {popupProps: PopupProps; showVersio
             this.unauthorizedSubscription = subscription;
         });
         const authSettings = await services.authService.settings();
+        if (authSettings.uiDefaultTheme) {
+            services.viewPreferences.setBackendDefaultTheme(authSettings.uiDefaultTheme);
+        }
         const {trackingID, anonymizeUsers} = authSettings.googleAnalytics || {trackingID: '', anonymizeUsers: true};
         const {loggedIn, username} = await services.users.get();
         if (trackingID) {
diff --git a/ui/src/app/shared/models.ts b/ui/src/app/shared/models.ts
index 4a8f4f542d3b7..98220bce78bee 100644
--- a/ui/src/app/shared/models.ts
+++ b/ui/src/app/shared/models.ts
@@ -609,6 +609,7 @@ export interface AuthSettings {
     userLoginsDisabled: boolean;
     kustomizeVersions: string[];
     uiCssURL: string;
+    uiDefaultTheme: string;
     uiBannerContent: string;
     uiBannerURL: string;
     uiBannerPermanent: boolean;
diff --git a/ui/src/app/shared/services/view-preferences-service.ts b/ui/src/app/shared/services/view-preferences-service.ts
index cff4aeb74b326..4a84d5e84f37f 100644
--- a/ui/src/app/shared/services/view-preferences-service.ts
+++ b/ui/src/app/shared/services/view-preferences-service.ts
@@ -204,6 +204,7 @@ const DEFAULT_PREFERENCES: ViewPreferences = {
 
 export class ViewPreferencesService {
     private preferencesSubj: BehaviorSubject<ViewPreferences>;
+    private backendDefaultTheme: string = '';
 
     public init() {
         if (!this.preferencesSubj) {
@@ -214,6 +215,12 @@ export class ViewPreferencesService {
         }
     }
 
+    public setBackendDefaultTheme(theme: string) {
+        this.backendDefaultTheme = theme;
+        // Reload preferences with the new backend default
+        this.preferencesSubj.next(this.loadPreferences());
+    }
+
     public getPreferences(): Observable<ViewPreferences> {
         return this.preferencesSubj;
     }
@@ -239,6 +246,11 @@ export class ViewPreferencesService {
         } else {
             preferences = DEFAULT_PREFERENCES;
         }
-        return deepMerge(DEFAULT_PREFERENCES, preferences);
+        const merged = deepMerge(DEFAULT_PREFERENCES, preferences);
+        // If backend default theme is set and user hasn't explicitly set a theme, use backend default
+        if (this.backendDefaultTheme && (!preferencesStr || !JSON.parse(preferencesStr).theme)) {
+            merged.theme = this.backendDefaultTheme;
+        }
+        return merged;
     }
 }
diff --git a/util/settings/settings.go b/util/settings/settings.go
index 52b4dcca4b526..384e2f138d48d 100644
--- a/util/settings/settings.go
+++ b/util/settings/settings.go
@@ -115,6 +115,8 @@ type ArgoCDSettings struct {
 	UiBannerPermanent bool `json:"uiBannerPermanent,omitempty"` //nolint:revive //FIXME(var-naming)
 	// Position of UI Banner
 	UiBannerPosition string `json:"uiBannerPosition,omitempty"` //nolint:revive //FIXME(var-naming)
+	// UiDefaultTheme holds the default theme for the UI (light, dark, auto)
+	UiDefaultTheme string `json:"uiDefaultTheme,omitempty"` //nolint:revive //FIXME(var-naming)
 	// PasswordPattern for password regular expression
 	PasswordPattern string `json:"passwordPattern,omitempty"`
 	// BinaryUrls contains the URLs for downloading argocd binaries
@@ -505,6 +507,8 @@ const (
 	settingUIBannerPermanentKey = "ui.bannerpermanent"
 	// settingUIBannerPositionKey designates the key for the position of the banner
 	settingUIBannerPositionKey = "ui.bannerposition"
+	// settingUIDefaultThemeKey designates the key for the default theme (light, dark, auto)
+	settingUIDefaultThemeKey = "ui.defaulttheme"
 	// settingsBinaryUrlsKey designates the key for the argocd binary URLs
 	settingsBinaryUrlsKey = "help.download"
 	// settingsApplicationInstanceLabelKey is the key to configure injected app instance label key
@@ -1473,6 +1477,7 @@ func updateSettingsFromConfigMap(settings *ArgoCDSettings, argoCDCM *corev1.Conf
 	settings.UiBannerContent = argoCDCM.Data[settingUIBannerContentKey]
 	settings.UiBannerPermanent = argoCDCM.Data[settingUIBannerPermanentKey] == "true"
 	settings.UiBannerPosition = argoCDCM.Data[settingUIBannerPositionKey]
+	settings.UiDefaultTheme = argoCDCM.Data[settingUIDefaultThemeKey]
 	settings.BinaryUrls = getDownloadBinaryUrlsFromConfigMap(argoCDCM)
 	if err := ValidateExternalURL(argoCDCM.Data[settingURLKey]); err != nil {
 		log.Warnf("Failed to validate URL in configmap: %v", err)
diff --git a/util/settings/settings_test.go b/util/settings/settings_test.go
index 30b694b43d037..b9adbeb87e98b 100644
--- a/util/settings/settings_test.go
+++ b/util/settings/settings_test.go
@@ -1017,6 +1017,44 @@ func TestSettingsManager_GetSettings(t *testing.T) {
 		require.NoError(t, err)
 		assert.Equal(t, time.Hour*10, s.UserSessionDuration)
 	})
+	t.Run("UiDefaultThemeNotProvided", func(t *testing.T) {
+		_, settingsManager := fixtures(t.Context(), map[string]string{}, func(secret *corev1.Secret) {
+			secret.Data["server.secretkey"] = []byte("test")
+		})
+		s, err := settingsManager.GetSettings()
+		require.NoError(t, err)
+		assert.Empty(t, s.UiDefaultTheme)
+	})
+	t.Run("UiDefaultThemeDark", func(t *testing.T) {
+		_, settingsManager := fixtures(t.Context(), map[string]string{
+			"ui.defaulttheme": "dark",
+		}, func(secret *corev1.Secret) {
+			secret.Data["server.secretkey"] = []byte("test")
+		})
+		s, err := settingsManager.GetSettings()
+		require.NoError(t, err)
+		assert.Equal(t, "dark", s.UiDefaultTheme)
+	})
+	t.Run("UiDefaultThemeLight", func(t *testing.T) {
+		_, settingsManager := fixtures(t.Context(), map[string]string{
+			"ui.defaulttheme": "light",
+		}, func(secret *corev1.Secret) {
+			secret.Data["server.secretkey"] = []byte("test")
+		})
+		s, err := settingsManager.GetSettings()
+		require.NoError(t, err)
+		assert.Equal(t, "light", s.UiDefaultTheme)
+	})
+	t.Run("UiDefaultThemeAuto", func(t *testing.T) {
+		_, settingsManager := fixtures(t.Context(), map[string]string{
+			"ui.defaulttheme": "auto",
+		}, func(secret *corev1.Secret) {
+			secret.Data["server.secretkey"] = []byte("test")
+		})
+		s, err := settingsManager.GetSettings()
+		require.NoError(t, err)
+		assert.Equal(t, "auto", s.UiDefaultTheme)
+	})
 }
 
 func TestGetOIDCConfig(t *testing.T) {