diff --git a/docs/api.md b/docs/api.md
index d01cc649ba..f56a34c856 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -112,6 +112,12 @@ what gets sent over the wire.*
 >>> url = URL("https://example.org/")
 >>> url.host
 'example.org'
+
+>>> from pydantic import HttpUrl
+>>> pydantic_url = HttpUrl("https://example.org/")
+>>> url = URL(pydantic_url)
+>>> url.host
+'example.org'
 ```
 
 * `def __init__(url, **kwargs)`
diff --git a/httpx/_urls.py b/httpx/_urls.py
index 147a8fa333..64c264cc77 100644
--- a/httpx/_urls.py
+++ b/httpx/_urls.py
@@ -6,12 +6,16 @@
 import idna
 
 from ._types import QueryParamTypes
-from ._urlparse import urlparse
+from ._urlparse import ParseResult, urlparse
 from ._utils import primitive_value_to_str
 
 __all__ = ["URL", "QueryParams"]
 
 
+class HasDunderStr(typing.Protocol):
+    def __str__(self) -> str: ...
+
+
 class URL:
     """
     url = httpx.URL("HTTPS://jo%40email.com:a%20secret@müller.de:1234/pa%20th?search=ab#anchorlink")
@@ -74,7 +78,9 @@ class URL:
       themselves.
     """
 
-    def __init__(self, url: URL | str = "", **kwargs: typing.Any) -> None:
+    def __init__(
+        self, url: URL | str | HasDunderStr = "", **kwargs: typing.Any
+    ) -> None:
         if kwargs:
             allowed = {
                 "scheme": str,
@@ -113,15 +119,11 @@ def __init__(self, url: URL | str = "", **kwargs: typing.Any) -> None:
                 params = kwargs.pop("params")
                 kwargs["query"] = None if not params else str(QueryParams(params))
 
-        if isinstance(url, str):
-            self._uri_reference = urlparse(url, **kwargs)
-        elif isinstance(url, URL):
+        self._uri_reference: ParseResult
+        if isinstance(url, URL):
             self._uri_reference = url._uri_reference.copy_with(**kwargs)
         else:
-            raise TypeError(
-                "Invalid type for url.  Expected str or httpx.URL,"
-                f" got {type(url)}: {url!r}"
-            )
+            self._uri_reference = urlparse(str(url), **kwargs)
 
     @property
     def scheme(self) -> str:
diff --git a/tests/models/test_url.py b/tests/models/test_url.py
index 03072e8f5c..493be272e8 100644
--- a/tests/models/test_url.py
+++ b/tests/models/test_url.py
@@ -452,19 +452,17 @@ def test_url_set():
     assert all(url in urls for url in url_set)
 
 
-# Tests for TypeErrors when instantiating `httpx.URL`.
-
+def test_custom_object_url():
+    class ExternalURLClass:
+        def __str__(self):
+            return "https://www.example.com/"
 
-def test_url_invalid_type():
-    """
-    Ensure that invalid types on `httpx.URL()` raise a `TypeError`.
-    """
+    url = ExternalURLClass()
+    httpx_url = httpx.URL(url)
+    assert httpx_url == "https://www.example.com/"
 
-    class ExternalURLClass:  # representing external URL class
-        pass
 
-    with pytest.raises(TypeError):
-        httpx.URL(ExternalURLClass())  # type: ignore
+# Tests for TypeErrors when instantiating `httpx.URL`.
 
 
 def test_url_with_invalid_component():