Lake Donuzlav (Russian and Ukrainian: Донузлав, Crimean Tatar: Doñuzlav), also referred to as Donuzlav Bay, is the deepest lake of Crimea (27 m, 89 ft) and biggest in Chornomorske Raion (47 km², 18 sq mi). It is a protected landscape and recreational park of the Autonomous Republic of Crimea.

The lake is as salty as the sea near its mouth but bottom springs make the water much less saline near the head.

Technically it is no longer a lake but rather a bay since 1961, when a 200-metre width canal was washed through the sandy peresyp separating it from the Black Sea, when the construction of a Soviet naval base [ru] started. The peresyp length is about 12 km (7.5 mi) with widths varying between 0.3 km (980 ft) to 1 km (3,300 ft).

Donuzlav is located in Chornomorske and Saky raions (districts) at the Tarkhankut Peninsula as well as Yevpatoria Municipality. Donuzlav is one of several lakes located around the peninsula.

The length of Donuzlav is 30 km (19 mi), a width is up to 8.5 km (5.3 mi), an area of 42 km² (16 sq mi) and a depth is up to 27 m (89 ft). It has several small bays. Banks are high, steep, and winding. At separate parts of the lake, a wetland vegetation is common (i.e. common reed, cattail, others).

In the upper portion of the lakes are located two dams for fish farming, in the mid portion is a naval base. On the banks there is a wind-powered energy station (Sakska Wind Farm [ru]) with 53 wind turbines.

To the lake are headed several gulches (semi-dried streams) among which are Staryi Donuzlav, Donuzlav, Chernushka, and Burnuk.

In the northern part there is a Donuzlav recreational park [ru] of area 2,335 hectares.