diff --git a/lib/linguist/languages.yml b/lib/linguist/languages.yml
index 5260fe757e..489143dd4f 100644
--- a/lib/linguist/languages.yml
+++ b/lib/linguist/languages.yml
@@ -3705,6 +3705,7 @@ Markdown:
   wrap: true
   extensions:
   - ".md"
+  - ".livemd"
   - ".markdown"
   - ".mdown"
   - ".mdwn"
diff --git a/samples/Markdown/livebook.livemd b/samples/Markdown/livebook.livemd
new file mode 100644
index 0000000000..58f3754f93
--- /dev/null
+++ b/samples/Markdown/livebook.livemd
@@ -0,0 +1,22 @@
+<!-- livebook:{"persist_outputs":true} -->
+
+# Sample Livebook
+
+## Section
+
+### Markdown
+
+Notebooks are .livemd files, a subset of Markdown with support for equations and annotations.
+
+<!-- livebook:{"livebook_object":"cell_input","name":"plus","type":"number","value":"1"} -->
+
+```elixir
+{plus, _} = IO.gets("plus") |> Integer.parse()
+
+[1, 2, 3]
+|> Enum.map(&(&1 + plus))
+```
+
+```output
+[2, 3, 4]
+```