Xuanwu Lake, Urban lake in Nanjing, China

Xuanwu Lake is a 3.78-square-kilometre lake in central Nanjing, bordered on its south and west by the Ming city wall. Five islands—Huan, Ying, Ling, Liang and Cui—are linked by arched bridges, and the lake's circumference is about 15 kilometres. Its main entrance is Xuanwu Gate, and Jiming Temple stands near the southwest shore.

The lake formed through geological processes and served as a naval training site during the Song Dynasty (960-1279). Later it became an important water space in Nanjing's history.

The five islets were renamed in 1935 after the world's continents, then given their present names: Huan for its curved shape, Ying for its many cherry trees, Ling for water caltrop, Liang for Prince Zhaoming's Liang Garden, and Cui for its bamboo. Liang Islet's Lake God Temple honours the elder Mao, whose advice led to east-west oriented archive halls.

The lake is easily accessible by metro and has walking paths that go around it. The best time to visit is during daytime when the paths are well-lit and there are other people around.

The lake's name comes from a Southern Dynasty legend of a black dragon, a tortoise-snake hybrid called Xuanwu, seen in the water. The lake has had many names, including Sangbo and Kunming Lake, and at times disappeared entirely, as when Emperor Wen of Sui ordered Nanjing razed in the 6th century and the lake vanished for over 200 years.