Claire, Lake (545 sq mi/1,412 sq km), NE Alta., W Canada, W of L. Athabaska, in Wood Buffalo Natl. Park; 40 mi/64 km long, 28 mi/45 km wide; 58°30'N 112°00'W. Drains E into L. Athabaska through Mamawi L. Formerly a deep lake, it is now much silted up.