Duke Mu (穆公) (died 621 BC), born Ying Renhao (嬴任好), was a ruler of the State of Qin from 659 or 660 to 621 BC in China. One of the Five Overlords of the Spring and Autumn Period, he greatly expanded the territory of Qin during the reign of King Xiang of Zhou.

He acquired many talented advisors, such as Baili Xi (百里奚), Jian Shu (蹇叔), Pi Bao (丕豹), and Gongsun (公孫).

He was the son of Duke De and the younger brother of Duke Cheng. He married the daughter of Duke Xian of Jin (獻), and married his daughter, Huaiying (懷嬴), to Duke Wen of Jin. He helped his son-in-law win the Battle of Chengpu, (城濮之戰) against Chu.

His posthumous name Mu means "reverent".