Cai E (simplified Chinese: 蔡锷; traditional Chinese: 蔡鍔; pinyin: Cài È; Wade–Giles: Ts'ai O; 18 December 1882 – 8 November 1916) was a Chinese revolutionary leader and general. He was born Cai Genyin (Chinese: 蔡艮寅; pinyin: Cài Gěnyín) in Shaoyang, Hunan, and his courtesy name was Songpo (Chinese: 松坡; pinyin: Sōngpō). Cai eventually became an influential warlord in Yunnan (Yunnan clique), and is best known for his role in challenging the imperial ambitions (Hongxian emperor) of Yuan Shikai during the Anti-Monarchy War.
Cai's name has also been romanised as Tsai Ao.