Sima Lun (traditional Chinese: 司馬倫; simplified Chinese: 司马伦; pinyin: Sīmǎ Lún; Wade–Giles: Ssu-ma Lun) (born before 250[7] – poisoned June 5, 301), courtesy name Ziyi (子彛), was titled the Prince of Zhao (趙王; 赵王; Zhào Wáng) and the usurper of the Jin Dynasty from February 3 to May 31, 301.
Around February or March 250, he was enfeoffed as Marquis of Anle Village,[9][10] and when Sima Zhao established the Five Feudal Ranks of Zhou in 264, his fief was changed to Viscount of Dong'an, and he was designated Remonstrating and Consulting Grandee.
During the early reign of Emperor Hui, on 19 September 291,[14] Sima Lun was placed in charge of the military command of Xu (徐州) and Yan (兖州) Provinces.
His chief strategist Sun Xiu was arrested and initially set to be executed, but was spared by his half-brother Sima Rong.
Lun then requested a high level office, but was rebuffed by Empress Jia's advisors Zhang Hua and Pei Wei.
Empress Jia, in jealousy, deposed the crown prince Sima Yu (born not of her, but of her husband's concubine Consort Xie Jiu) in February 300.
In order to appease those who might be angry at his usurpation, Sima Lun rewarded many people with honors.