diff --git a/custom_components/pyscript/decorators/webhook.py b/custom_components/pyscript/decorators/webhook.py
index 612476c..3db0a09 100644
--- a/custom_components/pyscript/decorators/webhook.py
+++ b/custom_components/pyscript/decorators/webhook.py
@@ -54,6 +54,7 @@ async def _handler(_hass, webhook_id, request):
         func_args = {
             "trigger_type": "webhook",
             "webhook_id": webhook_id,
+            "request": request,
         }
 
         if "json" in request.headers.get(hdrs.CONTENT_TYPE, ""):
diff --git a/custom_components/pyscript/eval.py b/custom_components/pyscript/eval.py
index 07d6310..8a9df38 100644
--- a/custom_components/pyscript/eval.py
+++ b/custom_components/pyscript/eval.py
@@ -78,6 +78,7 @@
     "payload",
     "payload_obj",
     "qos",
+    "request",
     "retain",
     "topic",
     "trigger_type",
diff --git a/custom_components/pyscript/stubs/pyscript_builtins.py b/custom_components/pyscript/stubs/pyscript_builtins.py
index c4b1736..ea75580 100644
--- a/custom_components/pyscript/stubs/pyscript_builtins.py
+++ b/custom_components/pyscript/stubs/pyscript_builtins.py
@@ -133,10 +133,12 @@ def webhook_trigger(
 
     Args:
         webhook_id: Webhook id to listen to.
-        str_expr: Optional expression evaluated against ``trigger_type``, ``webhook_id``, and ``payload``.
+        str_expr: Optional expression evaluated against ``trigger_type``, ``webhook_id``, ``request``, and ``payload``.
         local_only: If False, allow requests from anywhere on the internet.
         methods: HTTP methods to allow.
         kwargs: Extra keyword arguments merged into each invocation.
+
+    Trigger kwargs include ``trigger_type="webhook"``, ``webhook_id``, the parsed payload fields, and ``request`` (the underlying ``aiohttp.web.Request``).
     """
     ...
 
diff --git a/docs/reference.rst b/docs/reference.rst
index fc8992c..3b7c587 100644
--- a/docs/reference.rst
+++ b/docs/reference.rst
@@ -882,6 +882,7 @@ variables:
 - ``trigger_type`` is set to "webhook"
 - ``webhook_id`` is set to the webhook_id that was called.
 - ``payload`` is the data/json that was sent in the request returned as a dictionary.
+- ``request`` is the underlying ``aiohttp.web.Request``. Use it to inspect headers (e.g. for HMAC signature validation), the HTTP method, query string, or to re-read the raw body via ``await request.read()`` (the body is cached after pyscript parses it into ``payload``).
 
 When the ``@webhook_trigger`` occurs, those same variables are passed as keyword arguments to the function in case it needs them. Additional keyword parameters can be specified by setting the optional ``kwargs`` argument to a ``dict`` with the keywords and values.
 
@@ -895,6 +896,25 @@ An simple example looks like
 
 which if called using the curl command ``curl -X POST -d 'key1=xyz&key2=abc' hass_url/api/webhook/myid`` outputs ``It ran! {'key1': 'xyz', 'key2': 'abc'}, 10``
 
+To validate an HMAC signature on incoming requests, declare ``request`` in the function and read the raw body:
+
+.. code:: python
+
+  import hmac
+  import hashlib
+
+  SECRET = b"shared-secret"
+
+  @webhook_trigger("github")
+  def gh(payload, request):
+      sig = request.headers.get("X-Hub-Signature-256", "")
+      body = await request.read()
+      expected = "sha256=" + hmac.new(SECRET, body, hashlib.sha256).hexdigest()
+      if not hmac.compare_digest(sig, expected):
+          log.warning("bad signature, ignoring")
+          return
+      log.info(f"verified webhook: {payload}")
+
 NOTE: A webhook_id can only be used by either a built-in Home Assistant automation or pyscript, but not both. Trying to use the same webhook_id in both will result in an error.
 
 @state_active
diff --git a/tests/test_decorators.py b/tests/test_decorators.py
index 8350500..12224d4 100644
--- a/tests/test_decorators.py
+++ b/tests/test_decorators.py
@@ -10,8 +10,10 @@
 from custom_components.pyscript import trigger
 from custom_components.pyscript.const import DOMAIN
 from custom_components.pyscript.function import Function
+from homeassistant.components import webhook
 from homeassistant.const import EVENT_HOMEASSISTANT_STARTED, EVENT_STATE_CHANGED
 from homeassistant.setup import async_setup_component
+from homeassistant.util.aiohttp import MockRequest
 
 
 async def setup_script(hass, notify_q, now, source):
@@ -224,3 +226,33 @@ def func6(value):
         hass.states.async_set("pyscript.var1", 6 + 2 * i)
         seq_num += 1
         assert literal_eval(await wait_until_done(notify_q)) == [seq_num, 6 + 2 * i]
+
+
+@pytest.mark.asyncio
+async def test_webhook_request_kwarg(hass):
+    """The aiohttp request is passed to the user function as the `request` kwarg."""
+    notify_q = asyncio.Queue(0)
+    await setup_script(
+        hass,
+        notify_q,
+        [dt(2020, 7, 1, 11, 59, 59, 999999)],
+        """
+@webhook_trigger("test_req_hook")
+def webhook_test(payload, request):
+    pyscript.done = [request.headers["X-My-Sig"], request.method, payload]
+""",
+    )
+    hass.bus.async_fire(EVENT_HOMEASSISTANT_STARTED)
+    await hass.async_block_till_done()
+
+    request = MockRequest(
+        content=b'{"hello": "world"}',
+        mock_source="test",
+        method="POST",
+        headers={"Content-Type": "application/json", "X-My-Sig": "abc123"},
+        remote="127.0.0.1",
+    )
+
+    await webhook.async_handle_webhook(hass, "test_req_hook", request)
+
+    assert literal_eval(await wait_until_done(notify_q)) == ["abc123", "POST", {"hello": "world"}]