Zhao Dun 趙盾, personal name Ying Dun 嬴盾, posthumous title Zhao Xuanzi 趙宣子 or Xuan Meng 宣孟, was a nobleman in the state of Jin 晉 and a member of the house of Zhao 趙 during the Spring and Autumn period 春秋 (770-5th cent. BCE).
He was a son of Zhao Shuai 趙衰 (Zhao Chengzi 趙成子) and served the dukes Xiang 晉襄公 (r. 628-621) and Cheng 晉成公 (r. 607-600).
In 622, a whole generation of high ministers died: Zhao Shuai 趙衰, Luan Zhi 欒枝, Xian Qieju 先且居 and Xu Chenxiang 胥臣相. Duke Xiang thereupon reorganized the military system, created three armies (sanjun 三軍) and a new command structure. Zhao Dun was appointed marshal of the Central Army (zhongjun yuanshuai 中軍元帥), a position identical to that of counsellor-in-chief. The duke also issued administrative statutes and a penal code in order to create a more effective bureaucracy in the state of Jin.
When Duke Xiang died, Zhao Dun was sent to Qin 秦, where Prince Yong 雍 lived in exile. Yet at the same time, Jia Ji 賈季 supported Prince Le 樂 who lived in the state of Chen 陳. Zhao Dun did not shy away from having Prince Le assassinated on his way back to Jin. Yet the widow of late Duke Xiang desired to enthrone Prince Yigao 夷皋, who is known as Duke Ling 晉靈公 (r. 621-607), and won over Zhao Dun, who then even fought against the troops of Qin who escorted back Prince Yong. He defeated Qin in the battle of Linghu 令狐 (near modern Linyi 臨猗, Shanxi).
Duke Ling proved to be a tyrannic and incompetent ruler who rejected the remonstrations by his loyal ministers. Zhao Dun, inflamed by the wish to kill Duke Ling, was in 607 forced into exile, yet before he reached the border of Jin, his brother Zhao Chuan 趙穿 killed the tyrant. Prince Heitun 黑臀 was thereupon enthroned (i.e. Duke Cheng). The grand scribe (taishi 太史) of Jin, Dong Hu 董狐, injustly charged Zhao Dun with the murder of Duke Ling.