diff --git a/channels/routing.py b/channels/routing.py
index 07b5bab7..d09d5ffe 100644
--- a/channels/routing.py
+++ b/channels/routing.py
@@ -107,6 +107,15 @@ async def __call__(self, scope, receive, send):
         path = scope.get("path_remaining", scope.get("path", None))
         if path is None:
             raise ValueError("No 'path' key in connection scope, cannot route URLs")
+
+        if "path_remaining" not in scope:
+            # We are the outermost URLRouter, so handle root_path if present.
+            root_path = scope.get("root_path", "")
+            if root_path and not path.startswith(root_path):
+                # If root_path is present, path must start with it.
+                raise ValueError("No route found for path %r." % path)
+            path = path[len(root_path) :]
+
         # Remove leading / to match Django's handling
         path = path.lstrip("/")
         # Run through the routes we have until one matches
diff --git a/tests/test_routing.py b/tests/test_routing.py
index b41f652a..99c76790 100644
--- a/tests/test_routing.py
+++ b/tests/test_routing.py
@@ -107,6 +107,23 @@ async def test_url_router():
         "args": tuple(),
         "kwargs": {"default": 42},
     }
+    # Valid root_path in scope
+    assert (
+        await router(
+            {"type": "http", "path": "/root/", "root_path": "/root"}, None, None
+        )
+        == 1
+    )
+    assert (
+        await router(
+            {"type": "http", "path": "/root/foo/", "root_path": "/root"}, None, None
+        )
+        == 2
+    )
+
+    # Unmatched root_path in scope
+    with pytest.raises(ValueError):
+        await router({"type": "http", "path": "/", "root_path": "/root"}, None, None)
 
     # Invalid matches
     with pytest.raises(ValueError):
@@ -261,6 +278,29 @@ async def test_path_remaining():
         == 2
     )
 
+    assert (
+        await outermost_router(
+            {"type": "http", "path": "/root/prefix/stuff/", "root_path": "/root"},
+            None,
+            None,
+        )
+        == 2
+    )
+
+    with pytest.raises(ValueError):
+        await outermost_router(
+            {"type": "http", "path": "/root/root/prefix/stuff/", "root_path": "/root"},
+            None,
+            None,
+        )
+
+    with pytest.raises(ValueError):
+        await outermost_router(
+            {"type": "http", "path": "/root/prefix/root/stuff/", "root_path": "/root"},
+            None,
+            None,
+        )
+
 
 def test_invalid_routes():
     """