Lake Van is 119 kilometres (74 mi) across at its widest point, averaging a depth of 171 metres (560 ft) with a maximum recorded depth of 451 metres (1,480 ft). The lake surface lies 1,640 metres (5,400 ft) above sea level and the shore length is 430 kilometres (270 mi). Lake Van has an area of 3,755 km² (1,450 sq mi) and a volume of 607 cubic kilometres (146 cu mi).

The western portion of the lake is deepest, with a large basin deeper than 400 m (1,300 ft) lying northeast of Tatvan and south of Ahlat. The eastern arms of the lake are shallower. The Van-Ahtamar portion shelves gradually, with a maximum depth of about 250 m (820 ft) on its northwest side where it joins the rest of the lake. The Erciş arm is much shallower, mostly less than 50 m (160 ft), with a maximum depth of about 150 m (490 ft).

The lake water is strongly alkaline (pH 9.7–9.8) and rich in sodium carbonate and other salts, which are extracted by evaporation and used as detergents.

The lake was the centre of the Armenian kingdom of Ararat from about 1000 BC, afterwards of the Satrapy of Armina, Kingdom of Greater Armenia, and the Armenian Kingdom of Vaspurakan.

Along with Lake Sevan in today's Armenia and Lake Urmia in today's Iran, Van was one of the three great lakes of the Armenian Kingdom, referred to as the seas of Armenia (in ancient Assyrian sources: "tâmtu ša mât Nairi" (Upper Sea of Nairi), the Lower Sea being Lake Urmia). Over time, the lake was known by various Armenian names, including Armenian: Վանա լիճ (Lake of Van), Վանա ծով (Sea of Van), Արճեշի ծով (Sea of Arčeš), Բզնունեաց ծով (Sea of Bznunik), Ռշտունեաց ծով (Sea of Rshtunik), and Տոսպայ լիճ (Lake of Tosp).