diff --git a/c/sedona-geos/src/lib.rs b/c/sedona-geos/src/lib.rs
index cddf0585e..b9cdd5857 100644
--- a/c/sedona-geos/src/lib.rs
+++ b/c/sedona-geos/src/lib.rs
@@ -28,6 +28,7 @@ mod st_centroid;
 mod st_concavehull;
 mod st_convexhull;
 mod st_dwithin;
+mod st_exteriorring;
 mod st_isring;
 mod st_issimple;
 mod st_isvalid;
diff --git a/c/sedona-geos/src/register.rs b/c/sedona-geos/src/register.rs
index 82553bc29..f8ec66f9f 100644
--- a/c/sedona-geos/src/register.rs
+++ b/c/sedona-geos/src/register.rs
@@ -26,6 +26,7 @@ use crate::{
     st_concavehull::{st_concave_hull_allow_holes_impl, st_concave_hull_impl},
     st_convexhull::st_convex_hull_impl,
     st_dwithin::st_dwithin_impl,
+    st_exteriorring::st_exterior_ring_impl,
     st_isring::st_is_ring_impl,
     st_issimple::st_is_simple_impl,
     st_isvalid::st_is_valid_impl,
@@ -74,6 +75,7 @@ pub fn scalar_kernels() -> Vec<(&'static str, ScalarKernelRef)> {
         ("st_disjoint", st_disjoint_impl()),
         ("st_distance", st_distance_impl()),
         ("st_dwithin", st_dwithin_impl()),
+        ("st_exteriorring", st_exterior_ring_impl()),
         ("st_equals", st_equals_impl()),
         ("st_intersection", st_intersection_impl()),
         ("st_intersects", st_intersects_impl()),
diff --git a/c/sedona-geos/src/st_exteriorring.rs b/c/sedona-geos/src/st_exteriorring.rs
new file mode 100644
index 000000000..e7002c274
--- /dev/null
+++ b/c/sedona-geos/src/st_exteriorring.rs
@@ -0,0 +1,209 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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
+//
+//   http://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.
+
+use std::sync::Arc;
+
+use arrow_array::builder::BinaryBuilder;
+use datafusion_common::{error::Result, DataFusionError};
+use datafusion_expr::ColumnarValue;
+use geos::{Geom, Geometry, GeometryTypes};
+use sedona_expr::scalar_udf::{ScalarKernelRef, SedonaScalarKernel};
+use sedona_geometry::wkb_factory::WKB_MIN_PROBABLE_BYTES;
+use sedona_schema::{
+    datatypes::{SedonaType, WKB_GEOMETRY},
+    matchers::ArgMatcher,
+};
+
+use crate::executor::GeosExecutor;
+use crate::geos_to_wkb::write_geos_geometry;
+
+pub fn st_exterior_ring_impl() -> ScalarKernelRef {
+    Arc::new(STExteriorRing {})
+}
+
+#[derive(Debug)]
+struct STExteriorRing {}
+
+impl SedonaScalarKernel for STExteriorRing {
+    fn return_type(&self, args: &[SedonaType]) -> Result<Option<SedonaType>> {
+        let matcher = ArgMatcher::new(vec![ArgMatcher::is_geometry()], WKB_GEOMETRY);
+        matcher.match_args(args)
+    }
+
+    fn invoke_batch(
+        &self,
+        arg_types: &[SedonaType],
+        args: &[ColumnarValue],
+    ) -> Result<ColumnarValue> {
+        let executor = GeosExecutor::new(arg_types, args);
+        let mut builder = BinaryBuilder::with_capacity(
+            executor.num_iterations(),
+            WKB_MIN_PROBABLE_BYTES * executor.num_iterations(),
+        );
+
+        executor.execute_wkb_void(|maybe_geom| {
+            match maybe_geom {
+                Some(geom) => {
+                    invoke_scalar(&geom, &mut builder)?;
+                    builder.append_value([]);
+                }
+                None => builder.append_null(),
+            }
+            Ok(())
+        })?;
+
+        executor.finish(Arc::new(builder.finish()))
+    }
+}
+
+fn invoke_scalar(geom: &Geometry, writer: &mut BinaryBuilder) -> Result<()> {
+    let result = exterior_ring(geom)?;
+    write_geos_geometry(&result, writer)?;
+    Ok(())
+}
+
+/// Core exterior ring logic
+fn exterior_ring(geom: &Geometry) -> Result<Geometry> {
+    match geom.geometry_type() {
+        GeometryTypes::Polygon => {
+            let ring = geom.get_exterior_ring().map_err(|e| {
+                DataFusionError::Execution(format!("Failed to get exterior ring: {e}"))
+            })?;
+            Ok(Geom::clone(&ring))
+        }
+
+        GeometryTypes::MultiPolygon => {
+            let n = geom.get_num_geometries().map_err(|e| {
+                DataFusionError::Execution(format!("Failed to get polygon count: {e}"))
+            })?;
+
+            let mut rings: Vec<Geometry> = Vec::new();
+            for i in 0..n {
+                let poly = geom.get_geometry_n(i).map_err(|e| {
+                    DataFusionError::Execution(format!("Failed to get polygon {i}: {e}"))
+                })?;
+                let ring = poly.get_exterior_ring().map_err(|e| {
+                    DataFusionError::Execution(format!("Failed to get exterior ring: {e}"))
+                })?;
+                rings.push(Geom::clone(&ring));
+            }
+
+            if rings.is_empty() {
+                Geometry::create_geometry_collection(Vec::new()).map_err(|e| {
+                    DataFusionError::Execution(format!("Failed to create empty collection: {e}"))
+                })
+            } else if rings.len() == 1 {
+                Ok(rings.into_iter().next().unwrap())
+            } else {
+                Geometry::create_multiline_string(rings).map_err(|e| {
+                    DataFusionError::Execution(format!("Failed to create multilinestring: {e}"))
+                })
+            }
+        }
+
+        GeometryTypes::GeometryCollection => {
+            let n = geom.get_num_geometries().map_err(|e| {
+                DataFusionError::Execution(format!("Failed to get geometry count: {e}"))
+            })?;
+
+            let mut components: Vec<Geometry> = Vec::new();
+            for i in 0..n {
+                let child = geom.get_geometry_n(i).map_err(|e| {
+                    DataFusionError::Execution(format!("Failed to get geometry {i}: {e}"))
+                })?;
+                components.push(exterior_ring(&Geom::clone(&child))?);
+            }
+
+            Geometry::create_geometry_collection(components).map_err(|e| {
+                DataFusionError::Execution(format!("Failed to create geometry collection: {e}"))
+            })
+        }
+
+        // Non-area geometries → empty
+        _ => Geometry::create_geometry_collection(Vec::new()).map_err(|e| {
+            DataFusionError::Execution(format!("Failed to create empty geometry: {e}"))
+        }),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use rstest::rstest;
+    use sedona_expr::scalar_udf::SedonaScalarUDF;
+    use sedona_schema::datatypes::{SedonaType, WKB_GEOMETRY, WKB_VIEW_GEOMETRY};
+    use sedona_testing::compare::assert_array_equal;
+    use sedona_testing::create::create_array;
+    use sedona_testing::testers::ScalarUdfTester;
+
+    #[rstest]
+    fn udf(#[values(WKB_GEOMETRY, WKB_VIEW_GEOMETRY)] sedona_type: SedonaType) {
+        let udf = SedonaScalarUDF::from_kernel("st_exterior_ring", st_exteriorring_impl());
+        let tester = ScalarUdfTester::new(udf.into(), vec![sedona_type]);
+
+        tester.assert_return_type(WKB_GEOMETRY);
+
+        let result = tester
+            .invoke_scalar("POLYGON((0 0, 1 0, 1 1, 0 0))")
+            .unwrap();
+        tester.assert_scalar_result_equals(result, "LINESTRING (0 0, 1 0, 1 1, 0 0)");
+
+        let result = tester
+            .invoke_scalar(datafusion_common::ScalarValue::Null)
+            .unwrap();
+        assert!(result.is_null());
+
+        let input_wkt = vec![
+            Some("POINT(1 2)"),
+            Some("LINESTRING (0 0, 1 0, 0 1)"),
+            Some("MULTIPOINT (1 1, 2 2)"),
+            None,
+            Some("POLYGON((0 0, 10 0, 10 10, 0 10, 0 0))"),
+            Some("POLYGON Z ((0 0 1, 10 0 1, 10 10 1, 0 10 1, 0 0 1))"),
+            Some("POLYGON M ((0 0 5, 10 0 5, 10 10 5, 0 10 5, 0 0 5))"),
+            Some("POLYGON ZM ((0 0 1 9, 10 0 1 9, 10 10 1 9, 0 10 1 9, 0 0 1 9))"),
+            Some(
+                "MULTIPOLYGON(((0 0,0 1,1 1,1 0,0 0)),((10 10,10 11,11 11,11 10,10 10)))",
+            ),
+            Some(
+                "MULTIPOLYGON Z (((0 0 3,0 1 3,1 1 3,1 0 3,0 0 3)),((10 10 4,10 11 4,11 11 4,11 10 4,10 10 4)))",
+            ),
+        ];
+
+        let expected = create_array(
+            &[
+                None,
+                None,
+                None,
+                None,
+                Some("LINESTRING (0 0, 10 0, 10 10, 0 10, 0 0)"),
+                Some("LINESTRING Z (0 0 1, 10 0 1, 10 10 1, 0 10 1, 0 0 1)"),
+                Some("LINESTRING M (0 0 5, 10 0 5, 10 10 5, 0 10 5, 0 0 5)"),
+                Some("LINESTRING ZM (0 0 1 9, 10 0 1 9, 10 10 1 9, 0 10 1 9, 0 0 1 9)"),
+                Some(
+                    "MULTILINESTRING((0 0,0 1,1 1,1 0,0 0),(10 10,10 11,11 11,11 10,10 10))",
+                ),
+                Some(
+                    "MULTILINESTRING Z ((0 0 3,0 1 3,1 1 3,1 0 3,0 0 3),(10 10 4,10 11 4,11 11 4,11 10 4,10 10 4))",
+                ),
+            ],
+            &WKB_GEOMETRY,
+        );
+
+        assert_array_equal(&tester.invoke_wkb_array(input_wkt).unwrap(), &expected);
+    }
+}
diff --git a/c/sedona-s2geography/s2geography b/c/sedona-s2geography/s2geography
index c4d4e5f74..e63647cb4 160000
--- a/c/sedona-s2geography/s2geography
+++ b/c/sedona-s2geography/s2geography
@@ -1 +1 @@
-Subproject commit c4d4e5f7416dc203d3cb0485d56f5d72e9ccb6dd
+Subproject commit e63647cb4536648b06cc5aa6b97ce1777a5f6163
diff --git a/python/sedonadb/tests/functions/test_functions.py b/python/sedonadb/tests/functions/test_functions.py
index ff566cccf..28b267048 100644
--- a/python/sedonadb/tests/functions/test_functions.py
+++ b/python/sedonadb/tests/functions/test_functions.py
@@ -3365,3 +3365,63 @@ def test_st_NRings(eng, geom, expected):
         f"SELECT ST_NRings({geom_or_null(geom)})",
         expected,
     )
+
+
+@pytest.mark.parametrize("eng", [SedonaDB, PostGIS])
+@pytest.mark.parametrize(
+    ("geom", "expected"),
+    [
+        (None, None),
+        ("POINT EMPTY", None),
+        ("LINESTRING EMPTY", None),
+        ("POLYGON EMPTY", 0),
+        ("MULTIPOINT EMPTY", None),
+        ("MULTILINESTRING EMPTY", None),
+        ("MULTIPOLYGON EMPTY", None),
+        ("GEOMETRYCOLLECTION EMPTY", None),
+        ("POINT (1 2)", None),
+        ("MULTIPOINT ((0 0), (1 1))", None),
+        ("LINESTRING (0 0, 1 1, 2 2)", None),
+        ("MULTILINESTRING ((0 0, 1 1), (2 2, 3 3))", None),
+        ("POLYGON ((0 0, 1 0, 1 1, 0 1, 0 0))", "LINESTRING (0 0, 1 0, 1 1, 0 1, 0 0)"),
+        (
+            "POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0), (1 1, 1 2, 2 2, 2 1, 1 1))",
+            "LINESTRING (0 0, 10 0, 10 10, 0 10, 0 0)",
+        ),
+        (
+            "MULTIPOLYGON (((0 0, 1 0, 1 1, 0 1, 0 0)), ((10 10, 20 10, 20 20, 10 20, 10 10)))",
+            None,
+        ),
+        ("GEOMETRYCOLLECTION(POINT(1 1), POLYGON((0 0, 1 0, 1 1, 0 0)))", None),
+        (
+            "POLYGON Z ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1))",
+            "LINESTRING Z (0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)",
+        ),
+        (
+            "POLYGON Z ((0 0 10, 4 0 10, 4 4 10, 0 4 10, 0 0 10), (1 1 5, 1 2 5, 2 2 5, 2 1 5, 1 1 5))",
+            "LINESTRING Z (0 0 10, 4 0 10, 4 4 10, 0 4 10, 0 0 10)",
+        ),
+        ("POINT Z (1 1 5)", None),
+        (
+            "POLYGON M ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1))",
+            "LINESTRING M (0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)",
+        ),
+        (
+            "POLYGON M ((0 0 1, 4 0 2, 4 4 3, 0 4 4, 0 0 1), (1 1 6, 1 2 7, 2 2 8, 2 1 9, 1 1 6))",
+            "LINESTRING M (0 0 1, 4 0 2, 4 4 3, 0 4 4, 0 0 1)",
+        ),
+        ("LINESTRING M (0 0 1, 1 1 2)", None),
+        (
+            "POLYGON ZM ((0 0 1 2, 1 0 1 2, 1 1 1 2, 0 1 1 2, 0 0 1 2))",
+            "LINESTRING ZM (0 0 1 2, 1 0 1 2, 1 1 1 2, 0 1 1 2, 0 0 1 2)",
+        ),
+        (
+            "POLYGON ZM ((0 0 10 1, 4 0 10 2, 4 4 10 3, 0 4 10 4, 0 0 10 1), (1 1 5 6, 1 2 5 7, 2 2 5 8, 2 1 5 9, 1 1 5 6))",
+            "LINESTRING ZM (0 0 10 1, 4 0 10 2, 4 4 10 3, 0 4 10 4, 0 0 10 1)",
+        ),
+        ("POLYGON ZM EMPTY", None),
+    ],
+)
+def test_st_exteriorRing(eng, geom, expected):
+    eng = eng.create_or_skip()
+    eng.assert_query_result(f"SELECT ST_ExteriorRing({geom_or_null(geom)})", expected)