Cai Mao (? - 208)was a military general specializing in naval warfare during the late Han Dynasty era of Chinese history. He was from Xiangyang in Jing Province and originally served the warlord Liu Biao before joining Cao Cao's forces. He gained his status when his sister married Liu Biao.
Cai Mao initially suffered several defeats against the warlord Sun Jian. Liu Biao's advisor Kuai Liang insisted that Cai Mao be put to death for his failures, but Liu Biao refused.
When Liu Biao named his oldest son Liu Qi as his heir on his deathbed, Cai Mao and his nephew Zhang Yun wrote a forged will choosing Liu Biao's second son Liu Cong, because Liu Cong was married to Cai Mao's niece. Cai Mao then sent Liu Qi back to Jiangxia.
When Cao Cao marched on their territory with a huge army, Cai Mao and Zhang Yun surrendered and became Cao Cao's chief naval commanders against Sun Quan.
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