diff --git a/include/s0104_maximum_depth_of_binary_tree.hpp b/include/s0104_maximum_depth_of_binary_tree.hpp
new file mode 100644
index 0000000..e360194
--- /dev/null
+++ b/include/s0104_maximum_depth_of_binary_tree.hpp
@@ -0,0 +1,15 @@
+#ifndef S0104_MAXIMUM_DEPTH_OF_BINARY_TREE_HPP
+#define S0104_MAXIMUM_DEPTH_OF_BINARY_TREE_HPP
+
+#include <algorithm>
+
+#include "structures.hpp"
+
+using namespace std;
+
+class S0104 {
+ public:
+  int maxDepth(TreeNode* root);
+};
+
+#endif
diff --git a/src/s0104_maximum_depth_of_binary_tree.cpp b/src/s0104_maximum_depth_of_binary_tree.cpp
new file mode 100644
index 0000000..387b175
--- /dev/null
+++ b/src/s0104_maximum_depth_of_binary_tree.cpp
@@ -0,0 +1,6 @@
+#include "s0104_maximum_depth_of_binary_tree.hpp"
+
+int S0104::maxDepth(TreeNode* root) {
+  if (root == nullptr) return 0;
+  return max(maxDepth(root->left), maxDepth(root->right)) + 1;
+}