diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index e063fbff18..d6c8bac63d 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -22,6 +22,7 @@ Redis       8.6
 
 Fixed
 ~~~~~
+* Fix key value pairs with a ``/`` in the key name failing to be set, retrieved and deleted via the API and the CLI. ``st2client`` now URL encodes the key name in request URLs and the API router URL decodes path variables after route matching instead of before. #4789
 * Fix ``TypeError`` when displaying help for actions whose parameters have no ``description`` key. #6375
 * Fix utf-8 encode before checking paramter max size #6352
 * Fix stuck running workflow tasks #6398 (by @guzzijones12@gmail.com)
diff --git a/st2client/st2client/models/core.py b/st2client/st2client/models/core.py
index 633e57911f..2a40103119 100644
--- a/st2client/st2client/models/core.py
+++ b/st2client/st2client/models/core.py
@@ -69,6 +69,15 @@ def parse_api_response(response: requests.models.Response) -> dict:
     return data
 
 
+def _quote_url_path_segment(value):
+    """
+    Quote a single URL path segment (a resource id or name) so a value which
+    contains characters such as "/" stays inside one path segment and reaches
+    the API intact. Key value pair names, for example, may contain "/".
+    """
+    return urllib.parse.quote(str(value), safe="")
+
+
 class Resource(object):
 
     # An alias to use for the resource if different than the class name.
@@ -253,7 +262,10 @@ def get_all(self, **kwargs):
 
     @add_auth_token_to_kwargs_from_env
     def get_by_id(self, id, **kwargs):
-        url = "/%s/%s" % (self.resource.get_url_path_name(), id)
+        url = "/%s/%s" % (
+            self.resource.get_url_path_name(),
+            _quote_url_path_segment(id),
+        )
         response = self.client.get(url, **kwargs)
         if response.status_code == http_client.NOT_FOUND:
             return None
@@ -276,12 +288,16 @@ def get_property(self, id_, property_name, self_deserialize=True, **kwargs):
         if kwargs:
             url = "/%s/%s/%s/?%s" % (
                 self.resource.get_url_path_name(),
-                id_,
+                _quote_url_path_segment(id_),
                 property_name,
                 urllib.parse.urlencode(kwargs),
             )
         else:
-            url = "/%s/%s/%s/" % (self.resource.get_url_path_name(), id_, property_name)
+            url = "/%s/%s/%s/" % (
+                self.resource.get_url_path_name(),
+                _quote_url_path_segment(id_),
+                property_name,
+            )
 
         if token:
             response = self.client.get(url, token=token)
@@ -377,7 +393,10 @@ def create(self, instance, **kwargs):
 
     @add_auth_token_to_kwargs_from_env
     def update(self, instance, **kwargs):
-        url = "/%s/%s" % (self.resource.get_url_path_name(), instance.id)
+        url = "/%s/%s" % (
+            self.resource.get_url_path_name(),
+            _quote_url_path_segment(instance.id),
+        )
         response = self.client.put(url, instance.serialize(), **kwargs)
         if response.status_code != http_client.OK:
             self.handle_error(response)
@@ -386,7 +405,10 @@ def update(self, instance, **kwargs):
 
     @add_auth_token_to_kwargs_from_env
     def delete(self, instance, **kwargs):
-        url = "/%s/%s" % (self.resource.get_url_path_name(), instance.id)
+        url = "/%s/%s" % (
+            self.resource.get_url_path_name(),
+            _quote_url_path_segment(instance.id),
+        )
         response = self.client.delete(url, **kwargs)
 
         if response.status_code not in [
@@ -401,7 +423,10 @@ def delete(self, instance, **kwargs):
 
     @add_auth_token_to_kwargs_from_env
     def delete_action(self, instance, remove_files, **kwargs):
-        url = "/%s/%s" % (self.resource.get_url_path_name(), instance.id)
+        url = "/%s/%s" % (
+            self.resource.get_url_path_name(),
+            _quote_url_path_segment(instance.id),
+        )
         payload = {"remove_files": remove_files}
         response = self.client.delete(url, data=orjson.dumps(payload), **kwargs)
         if response.status_code not in [
@@ -437,7 +462,10 @@ def clone(
 
     @add_auth_token_to_kwargs_from_env
     def delete_by_id(self, instance_id, **kwargs):
-        url = "/%s/%s" % (self.resource.get_url_path_name(), instance_id)
+        url = "/%s/%s" % (
+            self.resource.get_url_path_name(),
+            _quote_url_path_segment(instance_id),
+        )
         response = self.client.delete(url, **kwargs)
         if response.status_code not in [
             http_client.OK,
@@ -906,7 +934,7 @@ def get_by_name(self, name, **kwargs):
 
         url = "/%s/%s/?%s" % (
             self.resource.get_url_path_name(),
-            name,
+            _quote_url_path_segment(name),
             urllib.parse.urlencode(params),
         )
 
diff --git a/st2client/tests/unit/test_models.py b/st2client/tests/unit/test_models.py
index 31e762eb81..cdd5406860 100644
--- a/st2client/tests/unit/test_models.py
+++ b/st2client/tests/unit/test_models.py
@@ -488,3 +488,45 @@ def test_resource_get_by_name(self):
         actual = resource.serialize()
         expected = json.loads(json.dumps(base.RESOURCES[0]))
         self.assertEqual(actual, expected)
+
+    def test_keyvalue_get_by_name_with_slash_in_name(self):
+        mgr = models.KeyValuePairResourceManager(
+            models.KeyValuePair, base.FAKE_ENDPOINT
+        )
+        response = base.FakeResponse(
+            json.dumps({"name": "foo/bar", "value": "value1"}), 200, "OK"
+        )
+        with mock.patch.object(
+            httpclient.HTTPClient, "get", mock.MagicMock(return_value=response)
+        ) as mock_get:
+            resource = mgr.get_by_name("foo/bar")
+
+        self.assertEqual(resource.name, "foo/bar")
+        self.assertEqual(mock_get.call_args[0][0], "/keys/foo%2Fbar/?")
+
+    def test_keyvalue_update_with_slash_in_name(self):
+        mgr = models.KeyValuePairResourceManager(
+            models.KeyValuePair, base.FAKE_ENDPOINT
+        )
+        instance = models.KeyValuePair(name="foo/bar", value="value1")
+        response = base.FakeResponse(
+            json.dumps({"name": "foo/bar", "value": "value1"}), 200, "OK"
+        )
+        with mock.patch.object(
+            httpclient.HTTPClient, "put", mock.MagicMock(return_value=response)
+        ) as mock_put:
+            mgr.update(instance)
+
+        self.assertEqual(mock_put.call_args[0][0], "/keys/foo%2Fbar")
+
+    def test_keyvalue_delete_by_id_with_slash_in_name(self):
+        mgr = models.KeyValuePairResourceManager(
+            models.KeyValuePair, base.FAKE_ENDPOINT
+        )
+        response = base.FakeResponse("", 204, "NO CONTENT")
+        with mock.patch.object(
+            httpclient.HTTPClient, "delete", mock.MagicMock(return_value=response)
+        ) as mock_delete:
+            mgr.delete_by_id("foo/bar")
+
+        self.assertEqual(mock_delete.call_args[0][0], "/keys/foo%2Fbar")
diff --git a/st2common/st2common/router.py b/st2common/st2common/router.py
index 75eece396a..fb3b02c974 100644
--- a/st2common/st2common/router.py
+++ b/st2common/st2common/router.py
@@ -269,11 +269,14 @@ def add_spec(self, spec, transforms):
             )
 
     def match(self, req):
-        # NOTE: webob.url_unquote doesn't work correctly under Python 3 when paths contain non-ascii
-        # characters. That method supposed to handle Python 2 and Python 3 compatibility, but it
-        # doesn't work correctly under Python 3.
+        # NOTE: The routes are matched against the URL encoded path and the
+        # extracted path variables are URL decoded afterwards. Decoding the
+        # whole path before matching would turn an escaped "/" ("%2F") inside
+        # a single path variable value (for example a key value pair name)
+        # into a real path separator, so such requests could never match
+        # their route.
         try:
-            path = urllib.parse.unquote(req.path)
+            path = req.path
         except Exception as e:
             # This exception being thrown indicates that the URL / path contains bad or incorrectly
             # URL escaped characters. Instead of returning this stack track + 500 error to the
@@ -316,6 +319,14 @@ def match(self, req):
         method = path_vars.pop("_api_method")
         endpoint = self.spec["paths"][path][method]
 
+        # NOTE: webob.url_unquote doesn't work correctly under Python 3 when paths contain non-ascii
+        # characters. That method supposed to handle Python 2 and Python 3 compatibility, but it
+        # doesn't work correctly under Python 3, so urllib.parse.unquote is used instead.
+        path_vars = {
+            name: urllib.parse.unquote(value) if isinstance(value, str) else value
+            for (name, value) in six.iteritems(path_vars)
+        }
+
         return endpoint, path_vars
 
     def __call__(self, req):
diff --git a/st2common/tests/unit/test_router.py b/st2common/tests/unit/test_router.py
new file mode 100644
index 0000000000..bf39677424
--- /dev/null
+++ b/st2common/tests/unit/test_router.py
@@ -0,0 +1,63 @@
+# Copyright 2026 The StackStorm 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
+#
+#     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.
+
+import unittest
+
+import mock
+
+from st2common.router import Router
+
+
+class RouterMatchTestCase(unittest.TestCase):
+    def _get_router(self):
+        router = Router(auth=False)
+        router.spec = {
+            "paths": {
+                "/api/v1/keys/{name}": {
+                    "get": {"operationId": "st2api.controllers.v1.keyvalue:get_one"}
+                }
+            }
+        }
+        mapper = router.routes.submapper(
+            _api_path="/api/v1/keys/{name}",
+            _api_method="get",
+            conditions={"method": ["GET"]},
+        )
+        mapper.connect(None, "/v1/keys/{name}")
+        return router
+
+    def _match(self, path):
+        request = mock.Mock()
+        request.path = path
+        request.environ = {"REQUEST_METHOD": "GET"}
+        return self._get_router().match(request)
+
+    def test_match_plain_name(self):
+        endpoint, path_vars = self._match("/v1/keys/key1")
+        self.assertEqual(path_vars, {"name": "key1"})
+
+    def test_match_name_with_escaped_slash(self):
+        # A key value pair name may contain "/". The client URL encodes it as
+        # "%2F" and the router must hand the decoded name to the controller
+        # instead of failing to match the route.
+        endpoint, path_vars = self._match("/v1/keys/foo%2Fbar")
+        self.assertEqual(path_vars, {"name": "foo/bar"})
+
+    def test_match_name_with_escaped_space(self):
+        endpoint, path_vars = self._match("/v1/keys/foo%20bar")
+        self.assertEqual(path_vars, {"name": "foo bar"})
+
+
+if __name__ == "__main__":
+    unittest.main()