The lake Hvalvatn (Icelandic pronunciation: [ˈkʰvalˌvahtn̥]) is situated east of Hvalfjörður in the western portion of Iceland. It lies to the east of the tuya Hvalfell [ˈkʰvalˌfɛtl̥]. The surface measures 4.1 km2 (1.6 sq mi), and its greatest depth is 180 m (590 ft).
Not far from Hvalvatn is Glymur, the second highest waterfall in the country. Hiking trails lead both to the lake and to the waterfall.