diff --git a/lib/mint/http.ex b/lib/mint/http.ex
index c1a092fa..f8ca9ec2 100644
--- a/lib/mint/http.ex
+++ b/lib/mint/http.ex
@@ -377,6 +377,26 @@ defmodule Mint.HTTP do
   def upgrade(old_transport, transport_state, scheme, hostname, port, opts),
     do: Mint.Negotiate.upgrade(old_transport, transport_state, scheme, hostname, port, opts)
 
+  @doc """
+  Returns the protocol used by the current connection.
+
+  ## Examples
+
+      iex> Mint.HTTP.protocol(%Mint.HTTP1{})
+      :http1
+
+      iex> Mint.HTTP.protocol(%Mint.HTTP2{})
+      :http2
+  """
+  if Version.compare(System.version(), "1.7.0") in [:eq, :gt] do
+    @doc since: "1.4.0"
+  end
+
+  @spec protocol(t()) :: :http1 | :http2
+  def protocol(%Mint.HTTP1{}), do: :http1
+  def protocol(%Mint.HTTP2{}), do: :http2
+  def protocol(%Mint.UnsafeProxy{state: internal_conn}), do: protocol(internal_conn)
+
   @doc false
   @impl true
   @spec initiate(
diff --git a/test/http_test.exs b/test/http_test.exs
new file mode 100644
index 00000000..70e307c2
--- /dev/null
+++ b/test/http_test.exs
@@ -0,0 +1,4 @@
+defmodule Mint.HTTPTest do
+  use ExUnit.Case, async: true
+  doctest Mint.HTTP
+end