diff --git a/src/requests/adapters.py b/src/requests/adapters.py
index 670c92767c..4c994fcb1e 100644
--- a/src/requests/adapters.py
+++ b/src/requests/adapters.py
@@ -40,6 +40,7 @@
     InvalidURL,
     ProxyError,
     ReadTimeout,
+    RequestException,
     RetryError,
     SSLError,
 )
@@ -682,15 +683,15 @@ def send(
         except _ProxyError as e:
             raise ProxyError(e)
 
-        except (_SSLError, _HTTPError) as e:
-            if isinstance(e, _SSLError):
+        except (_SSLError, _HTTPError) as err:
+            if isinstance(err, _SSLError):
                 # This branch is for urllib3 versions earlier than v1.22
-                raise SSLError(e, request=request)
-            elif isinstance(e, ReadTimeoutError):
-                raise ReadTimeout(e, request=request)
-            elif isinstance(e, _InvalidHeader):
-                raise InvalidHeader(e, request=request)
+                raise SSLError(err, request=request) from err
+            elif isinstance(err, ReadTimeoutError):
+                raise ReadTimeout(err, request=request) from err
+            elif isinstance(err, _InvalidHeader):
+                raise InvalidHeader(err, request=request) from err
             else:
-                raise
+                raise RequestException(err, request=request) from err
 
         return self.build_response(request, resp)
diff --git a/tests/test_adapters.py b/tests/test_adapters.py
index 6c55d5a130..fdda8418d9 100644
--- a/tests/test_adapters.py
+++ b/tests/test_adapters.py
@@ -1,4 +1,10 @@
+from unittest import mock
+
+import pytest
+from urllib3.exceptions import HTTPError as _HTTPError
+
 import requests.adapters
+from requests.exceptions import RequestException
 
 
 def test_request_url_trims_leading_path_separators():
@@ -6,3 +12,34 @@ def test_request_url_trims_leading_path_separators():
     a = requests.adapters.HTTPAdapter()
     p = requests.Request(method="GET", url="http://127.0.0.1:10000//v:h").prepare()
     assert "/v:h" == a.request_url(p, {})
+
+
+def test_unknown_httperror_wrapped_in_requestexception():
+    """Test that unknown urllib3 HTTPError types are wrapped in RequestException.
+    
+    When urllib3 raises an HTTPError that isn't explicitly
+    handled (not SSLError, ReadTimeoutError, or InvalidHeader), it should be
+    wrapped in RequestException rather than propagating as-is.
+    """
+    adapter = requests.adapters.HTTPAdapter()
+    request = requests.Request(method="GET", url="http://example.com").prepare()
+    
+    # Create a generic HTTPError that doesn't match any specific handled types
+    generic_http_error = _HTTPError("Unknown HTTP error from urllib3")
+    
+    # Mock the connection to raise our generic HTTPError
+    with mock.patch.object(
+        adapter, 'get_connection_with_tls_context'
+    ) as mock_get_conn:
+        mock_conn = mock.MagicMock()
+        mock_conn.urlopen.side_effect = generic_http_error
+        mock_get_conn.return_value = mock_conn
+        
+        # The exception should be catchable as RequestException
+        with pytest.raises(RequestException) as exc_info:
+            adapter.send(request)
+        
+        # Verify it wraps the original error
+        assert exc_info.value.request == request
+        # Verify exception chaining
+        assert exc_info.value.__cause__ == generic_http_error