diff --git a/markdown_it/main.py b/markdown_it/main.py
index dfa18189..e87a7a44 100644
--- a/markdown_it/main.py
+++ b/markdown_it/main.py
@@ -19,7 +19,7 @@
 from .parser_block import ParserBlock  # noqa F401
 from .parser_inline import ParserInline  # noqa F401
 from .rules_core.state_core import StateCore
-from .renderer import RendererHTML
+from .renderer import RendererHTML, RendererProtocol
 from .utils import OptionsDict
 
 try:
@@ -43,7 +43,7 @@ def __init__(
         config: Union[str, Mapping] = "commonmark",
         options_update: Optional[Mapping] = None,
         *,
-        renderer_cls=RendererHTML,
+        renderer_cls: Callable[["MarkdownIt"], RendererProtocol] = RendererHTML,
     ):
         """Main parser class
 
diff --git a/markdown_it/renderer.py b/markdown_it/renderer.py
index 9ffa94b0..9e9c7751 100644
--- a/markdown_it/renderer.py
+++ b/markdown_it/renderer.py
@@ -6,14 +6,34 @@ class Renderer
 rules if you create plugin and adds new token types.
 """
 import inspect
-from typing import MutableMapping, Optional, Sequence
+from typing import (
+    Any,
+    ClassVar,
+    MutableMapping,
+    Optional,
+    Sequence,
+)
 
 from .common.utils import unescapeAll, escapeHtml
 from .token import Token
 from .utils import OptionsDict
 
+try:
+    from typing import Protocol
+except ImportError:  # Python <3.8 doesn't have `Protocol` in the stdlib
+    from typing_extensions import Protocol  # type: ignore[misc]
 
-class RendererHTML:
+
+class RendererProtocol(Protocol):
+    __output__: ClassVar[str]
+
+    def render(
+        self, tokens: Sequence[Token], options: OptionsDict, env: MutableMapping
+    ) -> Any:
+        ...
+
+
+class RendererHTML(RendererProtocol):
     """Contains render rules for tokens. Can be updated and extended.
 
     Example:
diff --git a/setup.cfg b/setup.cfg
index 72564ba0..60929005 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -30,6 +30,7 @@ project_urls =
 packages = find:
 install_requires =
     attrs>=19,<21
+    typing_extensions>=3.7.4;python_version<'3.8'
 python_requires = ~=3.6
 include_package_data = True
 zip_safe = False