diff --git a/lib/ex_doc.ex b/lib/ex_doc.ex
index fbe26f60f..320733c02 100644
--- a/lib/ex_doc.ex
+++ b/lib/ex_doc.ex
@@ -3,6 +3,8 @@ defmodule ExDoc do
   Elixir Documentation System. ExDoc produces documentation for Elixir projects
   """
 
+  alias ExDoc.Markdown
+
   defmodule Config do
     @moduledoc """
     Configuration structure that holds all the available options for ExDoc
@@ -39,6 +41,7 @@ defmodule ExDoc do
       language: @default.language,
       logo: nil,
       main: nil,
+      markdown_processor: nil,
       output: @default.output,
       project: nil,
       retriever: @default.retriever,
@@ -67,6 +70,7 @@ defmodule ExDoc do
        language: String.t,
        logo: nil | Path.t,
        main: nil | String.t,
+       markdown_processor: nil | atom,
        output: nil | Path.t,
        project: nil | String.t,
        retriever: :atom,
@@ -102,6 +106,12 @@ defmodule ExDoc do
   # Builds configuration by merging `options`, and normalizing the options.
   @spec build_config(String.t, String.t, Keyword.t) :: ExDoc.Config.t
   defp build_config(project, vsn, options) do
+    # The app environment has priority over the mix config
+    processor_from_env = Markdown.get_markdown_processor_from_app_env()
+    if !processor_from_env && options[:markdown_processor] do
+      Markdown.set_markdown_processor(options[:markdown_processor])
+    end
+    # After this, we have no use for the :markdown processor option
     options = normalize_options(options)
     preconfig = %Config{
       project: project,
diff --git a/lib/ex_doc/markdown.ex b/lib/ex_doc/markdown.ex
index f747ab2c6..8030e3787 100644
--- a/lib/ex_doc/markdown.ex
+++ b/lib/ex_doc/markdown.ex
@@ -47,13 +47,23 @@ defmodule ExDoc.Markdown do
     bin
   end
 
+  @doc false
+  def get_markdown_processor_from_app_env do
+    Application.get_env(:ex_doc, @markdown_processor_key)
+  end
+
+  @doc false
+  def set_markdown_processor(processor) do
+    Application.put_env(:ex_doc, @markdown_processor_key, processor)
+  end
+
   defp get_markdown_processor do
     case Application.fetch_env(:ex_doc, @markdown_processor_key) do
       {:ok, processor} ->
         processor
       :error ->
         processor = find_markdown_processor() || raise_no_markdown_processor()
-        Application.put_env(:ex_doc, @markdown_processor_key, processor)
+        set_markdown_processor(processor)
         processor
     end
   end
diff --git a/lib/ex_doc/markdown/mocks.ex b/lib/ex_doc/markdown/mocks.ex
new file mode 100644
index 000000000..0c7fac1d0
--- /dev/null
+++ b/lib/ex_doc/markdown/mocks.ex
@@ -0,0 +1,18 @@
+defmodule ExDoc.Markdown.MockMarkdownProcessor.MockMarkdownProcessorError do
+    @moduledoc false
+
+    defexception message: "You're using a mock markdown processor"
+  end
+
+defmodule ExDoc.Markdown.MockMarkdownProcessor do
+  @moduledoc false
+
+  # To be used in only in testing
+
+  def to_html(_, _) do
+    # When we get an exception, we know this processor's been used
+    # This seems to be the easiest way to ensure we're choosing the right processor
+    # without instrumenting the code
+    raise ExDoc.Markdown.MockMarkdownProcessor.MockMarkdownProcessorError
+  end
+end
diff --git a/test/ex_doc/markdown_processor_option_test.exs b/test/ex_doc/markdown_processor_option_test.exs
new file mode 100644
index 000000000..f5a9d707c
--- /dev/null
+++ b/test/ex_doc/markdown_processor_option_test.exs
@@ -0,0 +1,84 @@
+defmodule ExDoc.MarkdownProcessorOptionTest do
+  use ExUnit.Case
+
+  alias ExDoc.Markdown.MockMarkdownProcessor
+  alias ExDoc.Markdown.MockMarkdownProcessor.MockMarkdownProcessorError
+
+  setup do
+    File.rm_rf(output_dir())
+    File.mkdir_p!(output_dir())
+  end
+
+  defp output_dir do
+    Path.expand("../../tmp/html", __DIR__)
+  end
+
+  defp beam_dir do
+    Path.expand("../../tmp/beam", __DIR__)
+  end
+
+  defp doc_config_markdown_processor_not_set do
+    [project: "Elixir",
+     version: "1.0.1",
+     formatter: "html",
+     assets: "test/tmp/html_assets",
+     output: output_dir(),
+     source_root: beam_dir(),
+     source_beam: beam_dir(),
+     logo: "test/fixtures/elixir.png",
+     extras: ["test/fixtures/README.md"]]
+  end
+
+  defp doc_config_markdown_processor_set do
+    # MockMarkdownProcessor will raise an exception if used to process files
+    # This exception will be our way to tell that someting's not right.
+    Keyword.put(doc_config_markdown_processor_not_set(),
+                :markdown_processor,
+                MockMarkdownProcessor)
+  end
+
+  def generate_docs(config) do
+    # A wrapper around the child process, so that we can use assert_raise below.
+    # Propagates the MockMarkdownProcessorError exception from the chid process.
+    # Raises a MockMarkdownProcessorError if the exception causes the child process to exit.
+    Process.flag(:trap_exit, true)
+    try do
+      ExDoc.generate_docs(config[:project], config[:version], config)
+    catch
+      # Raise the exception so that it can be captured by assert_raise
+      :exit, {{%MockMarkdownProcessorError{} = exception, _}, _} -> raise exception
+      # The purpose of these tests is to detect if the right markdown processor is used.
+      _ -> :ok
+    end
+  end
+
+  test "app env not set, markdown_processor option set" do
+    Application.delete_env(:ex_doc, :markdown_processor)
+    # ExDoc.Markdown should respect our choice and run the mock processor
+    assert_raise MockMarkdownProcessorError, fn ->
+      generate_docs doc_config_markdown_processor_set()
+    end
+  end
+
+  test "app env not set, markdown_processor option not set" do
+    Application.delete_env(:ex_doc, :markdown_processor)
+    generate_docs doc_config_markdown_processor_not_set()
+  end
+
+  test "app env set, markdown_processor option set" do
+    Application.put_env(:ex_doc, :markdown_processor, MockMarkdownProcessor)
+    # It's been given two mock processors
+    assert_raise MockMarkdownProcessorError, fn ->
+      generate_docs doc_config_markdown_processor_set()
+    end
+  end
+
+  test "app env set, markdown_processor option not set" do
+    Application.put_env(:ex_doc, :markdown_processor, MockMarkdownProcessor)
+    # The app env has priority
+    assert_raise MockMarkdownProcessorError, fn ->
+      generate_docs doc_config_markdown_processor_not_set()
+    end
+  end
+
+end