diff --git a/solution/0173.Binary Search Tree Iterator/Solution.java b/solution/0173.Binary Search Tree Iterator/Solution.java
new file mode 100644
index 0000000000000..a251b9cb1f613
--- /dev/null
+++ b/solution/0173.Binary Search Tree Iterator/Solution.java	
@@ -0,0 +1,50 @@
+public class Solution {
+
+    /**
+     * Definition for a binary tree node.
+     * public class TreeNode {
+     *     int val;
+     *     TreeNode left;
+     *     TreeNode right;
+     *     TreeNode(int x) { val = x; }
+     * }
+     */
+    class BSTIterator {
+
+        private TreeNode currentNode = null;
+        private Stack<TreeNode> stack = new Stack<TreeNode>();
+
+        public BSTIterator(TreeNode root) {
+            if (root != null) {
+                currentNode = root;
+            }
+        }
+
+        /** @return the next smallest number */
+        public int next() {
+            while (currentNode != null) {
+                stack.push(currentNode);
+                currentNode = currentNode.left;
+            }
+
+            currentNode = stack.pop();
+            TreeNode node = currentNode;
+            currentNode = currentNode.right;
+
+            return node.val;
+        }
+
+        /** @return whether we have a next smallest number */
+        public boolean hasNext() {
+            return currentNode != null || !stack.isEmpty();
+        }
+    }
+
+    /**
+     * Your BSTIterator object will be instantiated and called as such:
+     * BSTIterator obj = new BSTIterator(root);
+     * int param_1 = obj.next();
+     * boolean param_2 = obj.hasNext();
+     */
+    
+}