Dongting Lake, or Lake Dongting (Chinese: 洞庭湖; pinyin: Dòngtíng Hú; Wade–Giles: Tung-t'ing Hu) is a large, shallow lake in northeastern Hunan province, China. It is a flood basin of the Yangtze River (Chang Jiang). Hence the lake's size depends on the season. The provinces of Hubei and Hunan are named after their location relative to the lake: Hubei means "North of the Lake" and Hunan means "South of the Lake" in Chinese.

Dongting Lake is famous in Chinese culture as the place of origin of Dragon boat racing. It is the site of Junshan island, and is a home to the Finless Porpoise, which is endangered in China.

In the July–September period, flood water from the Yangtze flows into the lake, enlarging it greatly. The lake's area, which normally is 2,820 km² (data before 1998), may increase to 20,000 km² in flood season, when vast amounts of water and sediment from the Chang Jiang flow into the lake. The lake is also fed by four major rivers: the Xiang (湘), Zi (资), Yuan (沅) and Li (澧) rivers. Small rivers also flow in, the most famous one being Miluo River where a famous poet Qu Yuan committed suicide. In addition, the Xiao River(瀟) flows into the Xiang near Yongzhou, before the Xiang flows into the lake. Ocean-going vessels can travel through the Xiang to reach Changsha.