diff --git a/Libraries/LibJS/Runtime/ArrayPrototype.cpp b/Libraries/LibJS/Runtime/ArrayPrototype.cpp
index fc38b71acb6..d3e881d81de 100644
--- a/Libraries/LibJS/Runtime/ArrayPrototype.cpp
+++ b/Libraries/LibJS/Runtime/ArrayPrototype.cpp
@@ -53,6 +53,7 @@ ArrayPrototype::ArrayPrototype()
     put_native_function("join", join, 1);
     put_native_function("concat", concat, 1);
     put_native_function("slice", slice, 2);
+    put_native_function("indexOf", index_of, 1);
     put("length", Value(0));
 }
 
@@ -309,4 +310,37 @@ Value ArrayPrototype::slice(Interpreter& interpreter)
     return new_array;
 }
 
+Value ArrayPrototype::index_of(Interpreter& interpreter)
+{
+    auto* array = array_from(interpreter);
+    if (!array)
+        return {};
+
+    i32 array_size = static_cast<i32>(array->elements().size());
+    if (interpreter.argument_count() == 0 || array_size == 0)
+        return Value(-1);
+
+    i32 from_index = 0;
+    if (interpreter.argument_count() >= 2) {
+        from_index = interpreter.argument(1).to_number().to_i32();
+
+        if (from_index >= array_size)
+            return Value(-1);
+
+        auto negative_min_index = ((array_size - 1) * -1);
+        if (from_index < negative_min_index)
+            from_index = 0;
+        else if (from_index < 0)
+            from_index = (array_size - 1) + from_index;
+    }
+
+    auto search_element = interpreter.argument(0);
+    for (i32 i = from_index; i < array_size; ++i) {
+        auto& element = array->elements().at(i);
+        if (typed_eq(interpreter, element, search_element).as_bool())
+            return Value(i);
+    }
+
+    return Value(-1);
+}
 }
diff --git a/Libraries/LibJS/Runtime/ArrayPrototype.h b/Libraries/LibJS/Runtime/ArrayPrototype.h
index 5c27d3c9c7f..50afdced8b7 100644
--- a/Libraries/LibJS/Runtime/ArrayPrototype.h
+++ b/Libraries/LibJS/Runtime/ArrayPrototype.h
@@ -50,6 +50,6 @@ private:
     static Value join(Interpreter&);
     static Value concat(Interpreter&);
     static Value slice(Interpreter&);
+    static Value index_of(Interpreter&);
 };
-
 }
diff --git a/Libraries/LibJS/Tests/Array.prototype.indexOf.js b/Libraries/LibJS/Tests/Array.prototype.indexOf.js
new file mode 100644
index 00000000000..40e1f724403
--- /dev/null
+++ b/Libraries/LibJS/Tests/Array.prototype.indexOf.js
@@ -0,0 +1,24 @@
+load("test-common.js");
+
+try {
+    assert(Array.prototype.indexOf.length === 1);
+
+    var array = ['hello', 'friends', 1, 2, false];
+
+    assert(array.indexOf('hello') === 0);
+    assert(array.indexOf('friends') === 1);
+    assert(array.indexOf(false) === 4);
+    assert(array.indexOf(false, 2) === 4);
+    assert(array.indexOf(false, -2) === 4);
+    assert(array.indexOf(1) === 2);
+    assert(array.indexOf(1, 1000) === -1);
+    assert(array.indexOf(1, -1000) === 2);
+    assert(array.indexOf('serenity') === -1);
+    assert([].indexOf('serenity') === -1);
+    assert([].indexOf('serenity', 10) === -1);
+    assert([].indexOf('serenity', -10) === -1);
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}