diff --git a/CHANGES/11859.bugfix.rst b/CHANGES/11859.bugfix.rst
new file mode 100644
index 00000000000..1efb26813d7
--- /dev/null
+++ b/CHANGES/11859.bugfix.rst
@@ -0,0 +1 @@
+Removed support for ``ClientTimeout(total=0)`` to disable timeouts. Use ``None`` instead of ``0`` to disable the total timeout. Passing ``0`` now raises :exc:`ValueError` with a clear error message -- by :user:`veeceey`.
diff --git a/aiohttp/client.py b/aiohttp/client.py
index 26e67d490f2..555d5678d4d 100644
--- a/aiohttp/client.py
+++ b/aiohttp/client.py
@@ -240,6 +240,14 @@ class ClientTimeout:
     # - or use https://docs.python.org/3/library/dataclasses.html#dataclasses.replace
     # to overwrite the defaults
 
+    def __post_init__(self) -> None:
+        if self.total is not None and self.total == 0:
+            raise ValueError(
+                "total timeout must be a positive number or None to disable, "
+                "got 0. Using 0 to disable timeouts is no longer supported, "
+                "use None instead."
+            )
+
 
 # 5 Minute default read timeout
 DEFAULT_TIMEOUT: Final[ClientTimeout] = ClientTimeout(total=5 * 60, sock_connect=30)
diff --git a/requirements/constraints.txt b/requirements/constraints.txt
index 448d0df896a..2f83390aa74 100644
--- a/requirements/constraints.txt
+++ b/requirements/constraints.txt
@@ -69,7 +69,7 @@ exceptiongroup==1.3.1
     # via pytest
 execnet==2.1.2
     # via pytest-xdist
-filelock==3.21.2
+filelock==3.24.2
     # via virtualenv
 forbiddenfruit==0.1.4
     # via blockbuster
diff --git a/requirements/dev.txt b/requirements/dev.txt
index f5ad6cda8a9..da68c301905 100644
--- a/requirements/dev.txt
+++ b/requirements/dev.txt
@@ -67,7 +67,7 @@ exceptiongroup==1.3.1
     # via pytest
 execnet==2.1.2
     # via pytest-xdist
-filelock==3.21.2
+filelock==3.24.2
     # via virtualenv
 forbiddenfruit==0.1.4
     # via blockbuster
diff --git a/requirements/lint.txt b/requirements/lint.txt
index e35289588e1..a87b54907e4 100644
--- a/requirements/lint.txt
+++ b/requirements/lint.txt
@@ -29,7 +29,7 @@ distlib==0.4.0
     # via virtualenv
 exceptiongroup==1.3.1
     # via pytest
-filelock==3.21.2
+filelock==3.24.2
     # via virtualenv
 forbiddenfruit==0.1.4
     # via blockbuster
diff --git a/tests/test_connector.py b/tests/test_connector.py
index f73862e4d4c..cb156cef86b 100644
--- a/tests/test_connector.py
+++ b/tests/test_connector.py
@@ -1492,7 +1492,7 @@ def exception_handler(loop: asyncio.AbstractEventLoop, context: object) -> None:
         )
         m_resolver().resolve.return_value = dns_response_error()
         m_resolver().close = mock.AsyncMock()
-        f = loop.create_task(conn._create_direct_connection(req, [], ClientTimeout(0)))
+        f = loop.create_task(conn._create_direct_connection(req, [], ClientTimeout()))
 
         await asyncio.sleep(0)
         f.cancel()
@@ -2654,6 +2654,23 @@ async def test_start_tls_exception_with_ssl_shutdown_timeout_nonzero_pre_311(
     underlying_transport.abort.assert_not_called()
 
 
+def test_client_timeout_total_zero_raises() -> None:
+    """Test that ClientTimeout(total=0) raises ValueError.
+
+    Related to https://github.com/aio-libs/aiohttp/issues/11859
+    Using total=0 to disable timeouts is no longer supported in v4,
+    use None instead.
+    """
+    with pytest.raises(ValueError, match="total timeout must be a positive number"):
+        ClientTimeout(total=0)
+
+
+def test_client_timeout_total_none_is_valid() -> None:
+    """Test that ClientTimeout(total=None) is still valid for disabling timeouts."""
+    timeout = ClientTimeout(total=None)
+    assert timeout.total is None
+
+
 async def test_invalid_ssl_param() -> None:
     with pytest.raises(TypeError):
         aiohttp.TCPConnector(ssl=object())  # type: ignore[arg-type]