diff --git a/solutions/elixir/knapsack/1/lib/knapsack.ex b/solutions/elixir/knapsack/1/lib/knapsack.ex
new file mode 100644
index 0000000..c103cbb
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+++ b/solutions/elixir/knapsack/1/lib/knapsack.ex
@@ -0,0 +1,23 @@
+defmodule Knapsack do
+  @doc """
+  Return the maximum value that a knapsack can carry.
+  """
+  @spec maximum_value(items :: [%{value: integer, weight: integer}], maximum_weight :: integer) :: integer
+  def maximum_value(items, maximum_weight), do: knapsack(items, maximum_weight, 0)
+
+  # No items left
+  defp knapsack([], _, memo), do: memo
+
+  # Item too heavy
+  defp knapsack([item | items], remaining_capacity, memo) when item.weight > remaining_capacity do
+    knapsack(items, remaining_capacity, memo)
+  end
+
+  # Maxium between with and without the item
+  defp knapsack([item | items], remaining_capacity, memo) do
+    max(
+      knapsack(items, remaining_capacity - item.weight, memo + item.value),
+      knapsack(items, remaining_capacity, memo)
+    )
+  end
+end