Nansi Lake (Chinese: 南四湖; pinyin: Nánsì Hú; lit.

'Southern Four Lakes'), or Weishan Lake, administrated by Weishan County and located in Shandong Province in China, is the largest freshwater lake in the north of the country.

It consists of four connected lakes: Weishan (Chinese: 微山湖; pinyin: Wēishān Hú), Zhaoyang (Chinese: 昭阳湖; pinyin: Zhāoyáng Hú), Nanyang (Chinese: 南阳湖; pinyin: Nányáng Hú), Dushan (Chinese: 独山湖; pinyin: Dúshān Hú).

It is 120 km long and 1266 square km in area.

This Shandong location article is a stub.