diff --git a/asgiref/typing.py b/asgiref/typing.py
new file mode 100644
index 00000000..c2ec326e
--- /dev/null
+++ b/asgiref/typing.py
@@ -0,0 +1,202 @@
+from typing import Awaitable, Callable, Dict, Iterable, Optional, Tuple, Type, Union
+
+try:
+    from typing import Literal, Protocol, TypedDict
+except ImportError:
+    from typing_extensions import Literal, Protocol, TypedDict  # type: ignore
+
+
+class ASGIVersions(TypedDict, total=False):
+    spec_version: str
+    version: Union[Literal["2.0"], Literal["3.0"]]
+
+
+class HTTPScope(TypedDict):
+    type: Literal["http"]
+    asgi: ASGIVersions
+    http_version: str
+    method: str
+    scheme: str
+    path: str
+    raw_path: bytes
+    query_string: bytes
+    root_path: str
+    headers: Iterable[Tuple[bytes, bytes]]
+    client: Optional[Tuple[str, int]]
+    server: Optional[Tuple[str, Optional[int]]]
+    extensions: Dict[str, dict]
+
+
+class WebsocketScope(TypedDict):
+    type: Literal["websocket"]
+    asgi: ASGIVersions
+    http_version: str
+    scheme: str
+    path: str
+    raw_path: bytes
+    query_string: bytes
+    root_path: str
+    headers: Iterable[Tuple[bytes, bytes]]
+    client: Optional[Tuple[str, int]]
+    server: Optional[Tuple[str, Optional[int]]]
+    subprotocols: Iterable[str]
+    extensions: Dict[str, dict]
+
+
+class LifespanScope(TypedDict):
+    type: Literal["lifespan"]
+    asgi: ASGIVersions
+
+
+WWWScope = Union[HTTPScope, WebsocketScope]
+Scope = Union[HTTPScope, WebsocketScope, LifespanScope]
+
+
+class HTTPRequestEvent(TypedDict):
+    type: Literal["http.request"]
+    body: bytes
+    more_body: bool
+
+
+class HTTPResponseStartEvent(TypedDict):
+    type: Literal["http.response.start"]
+    status: int
+    headers: Iterable[Tuple[bytes, bytes]]
+
+
+class HTTPResponseBodyEvent(TypedDict):
+    type: Literal["http.response.body"]
+    body: bytes
+    more_body: bool
+
+
+class HTTPServerPushEvent(TypedDict):
+    type: Literal["http.response.push"]
+    path: str
+    headers: Iterable[Tuple[bytes, bytes]]
+
+
+class HTTPDisconnectEvent(TypedDict):
+    type: Literal["http.disconnect"]
+
+
+class WebsocketConnectEvent(TypedDict):
+    type: Literal["websocket.connect"]
+
+
+class WebsocketAcceptEvent(TypedDict):
+    type: Literal["websocket.accept"]
+    subprotocol: Optional[str]
+    headers: Iterable[Tuple[bytes, bytes]]
+
+
+class WebsocketReceiveEvent(TypedDict):
+    type: Literal["websocket.receive"]
+    bytes: Optional[bytes]
+    text: Optional[str]
+
+
+class WebsocketSendEvent(TypedDict):
+    type: Literal["websocket.send"]
+    bytes: Optional[bytes]
+    text: Optional[str]
+
+
+class WebsocketResponseStartEvent(TypedDict):
+    type: Literal["websocket.http.response.start"]
+    status: int
+    headers: Iterable[Tuple[bytes, bytes]]
+
+
+class WebsocketResponseBodyEvent(TypedDict):
+    type: Literal["websocket.http.response.body"]
+    body: bytes
+    more_body: bool
+
+
+class WebsocketDisconnectEvent(TypedDict):
+    type: Literal["websocket.disconnect"]
+    code: int
+
+
+class WebsocketCloseEvent(TypedDict):
+    type: Literal["websocket.close"]
+    code: Optional[int]
+
+
+class LifespanStartupEvent(TypedDict):
+    type: Literal["lifespan.startup"]
+
+
+class LifespanShutdownEvent(TypedDict):
+    type: Literal["lifespan.shutdown"]
+
+
+class LifespanStartupCompleteEvent(TypedDict):
+    type: Literal["lifespan.startup.complete"]
+
+
+class LifespanStartupFailedEvent(TypedDict):
+    type: Literal["lifespan.startup.failed"]
+    message: str
+
+
+class LifespanShutdownCompleteEvent(TypedDict):
+    type: Literal["lifespan.shutdown.complete"]
+
+
+class LifespanShutdownFailedEvent(TypedDict):
+    type: Literal["lifespan.shutdown.failed"]
+    message: str
+
+
+ASGIReceiveEvent = Union[
+    HTTPRequestEvent,
+    HTTPDisconnectEvent,
+    WebsocketConnectEvent,
+    WebsocketReceiveEvent,
+    WebsocketDisconnectEvent,
+    LifespanStartupEvent,
+    LifespanShutdownEvent,
+]
+
+
+ASGISendEvent = Union[
+    HTTPResponseStartEvent,
+    HTTPResponseBodyEvent,
+    HTTPServerPushEvent,
+    HTTPDisconnectEvent,
+    WebsocketAcceptEvent,
+    WebsocketSendEvent,
+    WebsocketResponseStartEvent,
+    WebsocketResponseBodyEvent,
+    WebsocketCloseEvent,
+    LifespanStartupCompleteEvent,
+    LifespanStartupFailedEvent,
+    LifespanShutdownCompleteEvent,
+    LifespanShutdownFailedEvent,
+]
+
+
+ASGIReceiveCallable = Callable[[], Awaitable[ASGIReceiveEvent]]
+ASGISendCallable = Callable[[ASGISendEvent], Awaitable[None]]
+
+
+class ASGI2Protocol(Protocol):
+    def __init__(self, scope: Scope) -> None:
+        ...
+
+    async def __call__(self, receive: ASGIReceiveCallable, send: ASGISendCallable) -> None:
+        ...
+
+
+ASGI2Framework = Type[ASGI2Protocol]
+ASGI3Framework = Callable[
+    [
+        Scope,
+        ASGIReceiveCallable,
+        ASGISendCallable,
+    ],
+    Awaitable[None],
+]
+ASGIFramework = Union[ASGI2Framework, ASGI3Framework]
diff --git a/setup.cfg b/setup.cfg
index b335e298..244ba7af 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -31,6 +31,8 @@ project_urls =
 python_requires = >=3.5
 packages = find:
 include_package_data = true
+install_requires =
+    typing_extensions; python_version < "3.8"
 zip_safe = false
 
 [options.extras_require]