diff --git a/src/main/scala/ninetyNineScalaProblems/Problem04.scala b/src/main/scala/ninetyNineScalaProblems/Problem04.scala
new file mode 100644
index 0000000..717e7c7
--- /dev/null
+++ b/src/main/scala/ninetyNineScalaProblems/Problem04.scala
@@ -0,0 +1,19 @@
+package ninetyNineScalaProblems
+
+import scala.annotation.tailrec
+
+object Problem04:
+    def listLength(list: List[Any]): Int =
+        @tailrec
+        def loop(cursor: List[Any], acc: Int): Int =
+            cursor match
+                case head :: tail =>
+                    loop(tail, acc + 1)
+                case Nil =>
+                    acc
+
+        loop(list, 0)
+
+object Problem04Stdlib:
+    def listLength(list: List[Any]): Int =
+        list.length
\ No newline at end of file
diff --git a/src/test/scala/ninetyNineScalaProblems/Problem04Suite.scala b/src/test/scala/ninetyNineScalaProblems/Problem04Suite.scala
new file mode 100644
index 0000000..56b831d
--- /dev/null
+++ b/src/test/scala/ninetyNineScalaProblems/Problem04Suite.scala
@@ -0,0 +1,12 @@
+package ninetyNineScalaProblems
+
+class Problem04Suite extends munit.FunSuite:
+    List(
+        (List(1, 2, 3, 4, 5), 5),
+        (List(1), 1),
+        (List(), 0)
+    ).foreach:
+        case (list, expected) =>
+            test(s"listLength returns [$expected]"):
+                assertEquals(Problem04.listLength(list), expected)
+                assertEquals(Problem04Stdlib.listLength(list), expected)
\ No newline at end of file