diff --git a/lib/elixir/lib/enum.ex b/lib/elixir/lib/enum.ex
index 12d21286fda..239cbb69d4a 100644
--- a/lib/elixir/lib/enum.ex
+++ b/lib/elixir/lib/enum.ex
@@ -3217,19 +3217,30 @@ defmodule Enum do
       iex> Enum.sum(1..10//2)
       25
 
+      iex> Enum.sum(1..10, & &1 * 2)
+      209
+
+      iex> Enum.sum([%{num: 1}, %{num: 2}], & &1.num)
+      3
+
+      iex> Enum.sum(%{num_2: 2, num_3: 3}, fn {_, v} -> v end)
+      5
   """
-  @spec sum(t) :: number
-  def sum(enumerable)
+  @spec sum(t, (element -> number)) :: number
+  def sum(enumerable, fun \\ fn item -> item end)
+
+  def sum(first..last//step, fun) do
+    first = fun.(first)
+    last = fun.(last)
 
-  def sum(first..last//step = range) do
-    range
+    first..last//step
     |> Range.size()
     |> Kernel.*(first + last - rem(last - first, step))
     |> div(2)
   end
 
-  def sum(enumerable) do
-    reduce(enumerable, 0, &+/2)
+  def sum(enumerable, fun) do
+    reduce(enumerable, 0, &(fun.(&1) + &2))
   end
 
   @doc """
diff --git a/lib/elixir/test/elixir/enum_test.exs b/lib/elixir/test/elixir/enum_test.exs
index 7269defd553..3ea9e184005 100644
--- a/lib/elixir/test/elixir/enum_test.exs
+++ b/lib/elixir/test/elixir/enum_test.exs
@@ -1254,6 +1254,39 @@ defmodule EnumTest do
     end
   end
 
+  test "sum/2" do
+    assert Enum.sum(
+             [%{number: 1, not_number: "foo"}, %{number: 2, not_number: "bar"}],
+             & &1.number
+           ) == 3
+
+    assert Enum.sum([%{number: 1}, %{number: 2}], &(&1.number * 2)) == 6
+    assert Enum.sum(%{num_1: 1, num_2: 2, num_3: 3}, fn {_, v} -> v end) == 6
+    assert Enum.sum(42..42, &(&1 * 2)) == 84
+    assert Enum.sum(42..42, &div(&1, 2)) == 21
+    assert Enum.sum(11..17, &(&1 * 2)) == 364
+    assert Enum.sum(11..17, &div(&1, 2)) == 26
+
+    assert_raise ArgumentError, fn ->
+      Enum.sum(11..17, &(&1 / 2))
+    end
+
+    assert_raise ArgumentError, fn ->
+      Enum.sum(42..42, &(&1 / 2))
+    end
+
+    assert_raise ArithmeticError, fn ->
+      Enum.sum(
+        [%{number: 1, not_number: "foo"}, %{number: 2, not_number: "bar"}],
+        & &1.not_number
+      )
+    end
+
+    assert_raise ArithmeticError, fn ->
+      Enum.sum(%{letter_a: "a", letter_b: "b", letter_c: "c"}, fn {_, v} -> v end)
+    end
+  end
+
   test "product/1" do
     assert Enum.product([]) == 1
     assert Enum.product([1]) == 1