Zhao Shuai 趙衰 (died 622 BCE), personal name Ying Shuai 嬴衰, courtesy name Zhao Ziyu 子余, also called Cheng Ji 成季 or Meng Ziyun 孟子余, posthumous title Zhao Chengzi 趙成子, was a nobleman in the state of Jin 晉 during the Spring and Autumn period 春秋 (770-5th cent. BCE), and ancestor to the house of Zhao 趙.
He was a younger brother of Zhao Su 趙夙 and a distant relative to the house of Qin 秦. He served from 633 to 622 as assistant commander of the Central Army (zhongjun zuo 中軍佐) under the dukes Wen 晉文公 (r. 637-628) and Xiang 晉襄公 (r. 628-621).
Zhao Shuai was a supporter of Prince Chong'er 重耳, the eventual Duke Wen, during the latter's 19 years in exile, and contributed to his successful return from the state of Qin as the main pretender to the throne. When Prince Chong'er became duke, Zhao Shuai was enfeoffed as a grand master (dafu 大夫) of Yuan 原 (modern Jiyuan 濟源, Henan), for which reason he is also known as Yuan Ji 原季.
Zhao Shuai was appointed highest commander of the new superior army (xin shangjun 新上軍) and in this position also functioned a chief minister of Jin. He critically contributed to the rise of Duke Wen to hegemonial lord (ba 霸) over the feudal lords of the Zhou empire 周 (11th cent.-221 BCE).
He also recommended competent nobles to the Duke, like Xian Zhen 先軫 or Luan Zhi 欒枝. In his military function, he defeated the army of Qin in 625 in the battle of Pengya 彭衙 (modern Chengcheng 澄城, Shaanxi).