曲沃桓叔（前802年 - 前731年），姬姓，名成师，谥为「桓」，晋国晋穆侯之子，曲沃的君主。

前745年晋昭侯把曲沃（在今中国山西省曲沃县）封给其叔成师，时年58岁，因「好德」而得民心。前739年晋大臣潘父弑杀了晋昭侯，迎立曲沃桓叔。桓叔欲入晋，晋人发兵攻桓叔，桓叔退回曲沃。晋人共立昭侯子公子平为君，是为孝侯。前731年曲沃桓叔去世。

桓叔之孙曲沃武公起兵灭晋，世称晋武公，从此曲沃与晋国合并。桓叔庶子韩武子，乃战国七雄的韩国的先祖。

Huan Shu of Quwo (曲沃桓叔 Qūwò Huán Shū|l=Uncle Huan of Quwo; 802–731 BC), personal name Ji Chengshi, was the first ruler of the Quwo (曲沃) state, a fief of the Jin state. He was a son of Marquis Mu of Jin and the younger brother of Marquis Wen of Jin. He was also uncle of Marquis Zhao of Jin, who granted him the land of Quwo.

In 745 BC, Marquis Zhao of Jin enfeoffed Huan Shu at Quwo (around modern-day Quwo County, Shanxi). He was said to be a benevolent ruler beloved by the people of Quwo.

In 739 BC, Jin official Panfu (潘父) murdered Marquis Zhao of Jin and invited Huan Shu to ascend the throne of Jin. However, Huan Shu was defeated by Jin troops and retreated to Quwo.

In 731 BC, Huan Shu died and was succeeded by his son, Count Zhuang of Quwo, to the Quwo throne. Another son of Huan Shu, Viscount Wu of Han, became the progenitor of the ruling house of the Han state.