Erhai or Er Lake (Chinese: 洱海; pinyin: Ěrhǎi), is an alpine fault lake in Dali City, Dali Prefecture, Yunnan province, China.

Erhai was also known as Yeyuze (叶榆泽) or Kunming Lake (昆明池) in ancient times.

In the following time, Chinese literature recorded the name "昆弥" as "昆弭" (Kun-mi) that "弭" is a rebus of "弥".

And the name of the lake was also changed to the character "渳" (mi) which has a water-meaning radical (氵) attached to it.

[1]: 45 According to Bai scholar's research, the "Yeyu" in the Chinese name "Yeyuze" (ze [泽] means lake) is evolved from Bai language which means "lower water", the pronunciation written in IPA as /jɛ33ji33/.

Highlights include Erhai Park and the Butterfly Springs on the Western bank.

It is one of three major Yunnan lakes with a high number of endemics, the two other being Fuxian and Dian (Dianchi).