diff --git a/ecosystem-explorer/src/v1/components/layout/sub-nav.test.tsx b/ecosystem-explorer/src/v1/components/layout/sub-nav.test.tsx
new file mode 100644
index 000000000..f3828ac62
--- /dev/null
+++ b/ecosystem-explorer/src/v1/components/layout/sub-nav.test.tsx
@@ -0,0 +1,81 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import { render, screen } from "@testing-library/react";
+import { MemoryRouter } from "react-router-dom";
+import { describe, it, expect } from "vitest";
+import { SubNav } from "./sub-nav";
+
+function renderSubNav(props: Parameters<typeof SubNav>[0]) {
+  return render(
+    <MemoryRouter>
+      <SubNav {...props} />
+    </MemoryRouter>
+  );
+}
+
+describe("SubNav", () => {
+  it("renders nothing when both crumbs and actions are empty", () => {
+    const { container } = renderSubNav({ crumbs: [] });
+    expect(container.firstChild).toBeNull();
+  });
+
+  it("renders breadcrumb landmark with each crumb in order", () => {
+    renderSubNav({
+      crumbs: [
+        { label: "Collector", href: "/collector" },
+        { label: "Components", href: "/collector/components" },
+        { label: "otlp" },
+      ],
+    });
+
+    const nav = screen.getByRole("navigation", { name: /breadcrumb/i });
+    expect(nav).toBeInTheDocument();
+
+    expect(screen.getByRole("link", { name: "Collector" })).toHaveAttribute("href", "/collector");
+    expect(screen.getByRole("link", { name: "Components" })).toHaveAttribute(
+      "href",
+      "/collector/components"
+    );
+    expect(screen.getByText("otlp")).toHaveAttribute("aria-current", "page");
+  });
+
+  it("renders the last crumb as a non-link with aria-current=page", () => {
+    renderSubNav({
+      crumbs: [{ label: "Home", href: "/" }, { label: "Detail" }],
+    });
+
+    expect(screen.queryByRole("link", { name: "Detail" })).toBeNull();
+    expect(screen.getByText("Detail")).toHaveAttribute("aria-current", "page");
+  });
+
+  it("renders actions in the right-aligned slot", () => {
+    renderSubNav({
+      crumbs: [{ label: "Home", href: "/" }],
+      actions: <button type="button">Filter</button>,
+    });
+
+    expect(screen.getByRole("button", { name: "Filter" })).toBeInTheDocument();
+  });
+
+  it("renders actions even when there are no crumbs", () => {
+    renderSubNav({
+      crumbs: [],
+      actions: <button type="button">Edit</button>,
+    });
+
+    expect(screen.getByRole("button", { name: "Edit" })).toBeInTheDocument();
+  });
+});
diff --git a/ecosystem-explorer/src/v1/components/layout/sub-nav.tsx b/ecosystem-explorer/src/v1/components/layout/sub-nav.tsx
new file mode 100644
index 000000000..805545432
--- /dev/null
+++ b/ecosystem-explorer/src/v1/components/layout/sub-nav.tsx
@@ -0,0 +1,82 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ * SubNav — breadcrumb row that sits below the navbar on inner pages.
+ *
+ * Mirrors opentelemetry.io's `.breadcrumb` pattern (Bootstrap), but tightened
+ * to the explorer's chrome. The right-side `actions` slot is for page-level
+ * controls (filter toggles, "Edit on GitHub", etc.). Renders nothing if both
+ * `crumbs` and `actions` are empty so callers can mount it unconditionally.
+ */
+import { ChevronRight } from "lucide-react";
+import { Link } from "react-router-dom";
+
+export interface BreadcrumbItem {
+  label: string;
+  href?: string;
+}
+
+export interface SubNavProps {
+  crumbs: BreadcrumbItem[];
+  actions?: React.ReactNode;
+  className?: string;
+}
+
+export function SubNav({ crumbs, actions, className }: SubNavProps) {
+  if (crumbs.length === 0 && !actions) return null;
+
+  return (
+    <div className={className ? `td-subnav ${className}` : "td-subnav"}>
+      <div className="td-subnav__container">
+        {crumbs.length > 0 && (
+          <nav className="td-subnav__breadcrumb" aria-label="Breadcrumb">
+            <ol className="td-subnav__crumbs">
+              {crumbs.map((crumb, idx) => {
+                const isLast = idx === crumbs.length - 1;
+                const ariaCurrent = isLast ? "page" : undefined;
+                return (
+                  <li key={idx} className="td-subnav__crumb">
+                    {idx > 0 && (
+                      <ChevronRight
+                        className="td-subnav__separator"
+                        aria-hidden
+                        focusable="false"
+                      />
+                    )}
+                    {isLast || !crumb.href ? (
+                      <span
+                        className="td-subnav__crumb-label td-subnav__crumb-label--current"
+                        aria-current={ariaCurrent}
+                      >
+                        {crumb.label}
+                      </span>
+                    ) : (
+                      <Link to={crumb.href} className="td-subnav__crumb-label">
+                        {crumb.label}
+                      </Link>
+                    )}
+                  </li>
+                );
+              })}
+            </ol>
+          </nav>
+        )}
+        {actions && <div className="td-subnav__actions">{actions}</div>}
+      </div>
+    </div>
+  );
+}
diff --git a/ecosystem-explorer/src/v1/styles/index.css b/ecosystem-explorer/src/v1/styles/index.css
index eb65f3ccf..f8e2746c4 100644
--- a/ecosystem-explorer/src/v1/styles/index.css
+++ b/ecosystem-explorer/src/v1/styles/index.css
@@ -20,11 +20,13 @@
  * - tokens.css       — v1-only surface-token overrides, scoped via `.v1-app`
  * - navbar.css       — v1 navbar (`.td-navbar`) — mirrors opentelemetry.io
  * - theme-toggle.css — v1 theme toggle dropdown — mirrors opentelemetry.io
+ * - sub-nav.css      — v1 breadcrumb sub-nav row beneath the navbar
  *
- * Navbar and theme-toggle styles use class selectors (`.td-navbar`,
+ * All v1 styles use class selectors (`.td-navbar`, `.td-subnav`,
  * `.td-light-dark-menu__*`) and only match elements rendered by `<V1App />`,
  * so they're inert in the legacy bundle even when both branches ship.
  */
 @import "./tokens.css";
 @import "./navbar.css";
 @import "./theme-toggle.css";
+@import "./sub-nav.css";
diff --git a/ecosystem-explorer/src/v1/styles/sub-nav.css b/ecosystem-explorer/src/v1/styles/sub-nav.css
new file mode 100644
index 000000000..25755a239
--- /dev/null
+++ b/ecosystem-explorer/src/v1/styles/sub-nav.css
@@ -0,0 +1,93 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/* Pixel-anchored at 16px-rem like the rest of v1 chrome. */
+
+.td-subnav {
+  font-size: 16px;
+  background-color: hsl(var(--card-hsl));
+  border-bottom: 1px solid hsl(var(--border-hsl));
+}
+
+.td-subnav__container {
+  width: 100%;
+  max-width: 1320px;
+  margin: 0 auto;
+  padding: 0.5rem 1.5rem;
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 1rem;
+  min-height: 2.5rem;
+  flex-wrap: wrap;
+}
+
+.td-subnav__breadcrumb {
+  min-width: 0;
+}
+
+.td-subnav__crumbs {
+  list-style: none;
+  margin: 0;
+  padding: 0;
+  display: flex;
+  flex-wrap: wrap;
+  align-items: center;
+  gap: 0.25rem;
+  font-size: 0.875rem;
+  line-height: 1.25;
+}
+
+.td-subnav__crumb {
+  display: inline-flex;
+  align-items: center;
+  gap: 0.25rem;
+}
+
+.td-subnav__separator {
+  width: 0.875rem;
+  height: 0.875rem;
+  color: hsl(var(--muted-foreground-hsl));
+  flex-shrink: 0;
+}
+
+.td-subnav__crumb-label {
+  color: hsl(var(--muted-foreground-hsl));
+  text-decoration: none;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  max-width: 24rem;
+}
+
+.td-subnav__crumb-label:hover,
+.td-subnav__crumb-label:focus-visible {
+  color: hsl(var(--foreground-hsl));
+  text-decoration: underline;
+  text-underline-offset: 0.2em;
+}
+
+.td-subnav__crumb-label--current {
+  color: hsl(var(--foreground-hsl));
+  font-weight: 600;
+}
+
+.td-subnav__actions {
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+  flex-shrink: 0;
+}