diff --git a/01_introduction_to_algorithms/ruby/01_binary_search.rb b/01_introduction_to_algorithms/ruby/01_binary_search.rb
new file mode 100644
index 0000000..33762ad
--- /dev/null
+++ b/01_introduction_to_algorithms/ruby/01_binary_search.rb
@@ -0,0 +1,26 @@
+def binary_search(list, item)
+  low = 0
+  high = list.length - 1
+
+  while low <= high
+    mid = (low + high) / 2
+    guess = list[mid]
+
+    if guess == item
+      return mid
+    elsif guess > item
+      high = mid - 1
+    else
+      low = mid + 1
+    end
+  end
+  
+  return nil
+end
+
+my_list = [1, 3, 5, 7, 9]
+puts binary_search(my_list, 3) # => 1
+
+# We need to use .inspect here because just printing nil
+# would output an empty string
+puts binary_search(my_list, -1).inspect # => nil