diff --git a/medium/length_of_longest_fibonacci_subsequence.py b/medium/length_of_longest_fibonacci_subsequence.py
new file mode 100644
index 0000000..28eb7fb
--- /dev/null
+++ b/medium/length_of_longest_fibonacci_subsequence.py
@@ -0,0 +1,18 @@
+# https://leetcode.com/problems/length-of-longest-fibonacci-subsequence
+
+from typing import Dict, List, Tuple
+
+class Solution:
+    def lenLongestFibSubseq(self, arr: List[int]) -> int:
+        indexes: Dict[int, int] = {num: i for i, num in enumerate(arr)}
+        d: Dict[Tuple[int, int], int] = {}
+        result = 0
+
+        for i in range(len(arr)):
+            for j in range(i):
+                k = indexes.get(arr[i] - arr[j])
+                if k is not None and k < j:
+                    d[j, i] = d.get((k, j), 2) + 1
+                    result = max(result, d[j, i])
+        return result
+