Sima Gui (; 235 - 11 March 274), courtesy name Zizhang (子璋),(高阳元王珪，字子璋，...) Jin Shu, vol.37 posthumously known as Prince Yuan of Gaoyang, was an imperial prince of the Western Jin dynasty. He was the seventh son of Sima Fu,([孚]九子：邕、望、辅、翼、晃、瑰、珪、衡、景。) Jin Shu, vol.37 Prince Xian of Anping and a younger brother of Sima Yi, regent of the Cao Wei state during the Three Kingdoms era.
Life Sima Gui was born in 235 to Sima Fu during the reign of Cao Rui. At the time, both his father and uncle Sima Yi were officials of Cao Wei. Gui was also born late in Sima Fu's life, as Fu was about 55 years old and his eldest son Sima Wang was about 30 years older than Gui. The Sima clan's prominence grew in the aftermath of the Incident at the Gaoping Tombs in February 249, as Sima Yi became sole regent; Yi's sons Sima Shi and Sima Zhao were also regents of Cao Wei. During the Cao Wei era, Sima Gui was appointed Marquis of Gaoyang Village. After Sima Zhao reinstated the "five-rank peerage" system in 264, Gui's title became Viscount of Zhenyang.(魏高阳乡侯。历河南令，进封浈阳子，...) Jin Shu, vol.37
In September 265, Gui's cousin Sima Zhao died. A few months later, on 8 February 266,bing'yin day of the 12th month of the 1st year of the Tai'shi era, per vol.79 of Zizhi Tongjian Sima Zhao's son Sima Yan (posthumously known as Emperor Wu of Jin) usurped the throne from Cao Huan and founded the Jin dynasty. The next day, Sima Gui, his brothers, father and nephews Sima Hong (司马洪; father of Sima Wei) and Sima Mao were made princes. Gui's fiefdom consisted of 5570 households.(邑五千五百七十户。) Jin Shu, vol.37
On 10 April 271,gui'si day of the 3rd month of the 7th year of the Tai'shi era, per Emperor Wu's biography in Book of Jin Emperor Wu appointed Wang Ye and Sima Gui as the Left and Right Supervisors of the Masters of Writing respectively.While Book of Jin recorded that Sima Gui was made Right Supervisor, Jin Zhu Gong Zan recorded him as the Left Supervisor. Jin Qi Ju Zhu (《晋起居注》; cited by vol.211 of Taiping Yulan) also recorded that Gui was made Right Supervisor. As Supervisor of the Masters of Writing, Sima Gui once submitted a petition by Jia Chong against his political rival Ren Kai (任恺), accusing Ren of being extravagant. This caused Ren to be relieved of his post.(充与荀勖、冯𬘘承间浸润，谓恺豪侈，用御食器。充遣尚书右仆射、高阳王珪奏恺，遂免官。) Jin Shu, vol.45
Sima Gui died without issue in March 274, just less than two years after his father's death in April 272. Gui had an excellent reputation, and he was deeply missed by Emperor Wu.(珪有美誉于世，而帝甚悼惜之。) Jin Shu, vol.37 The next day,Jin Shu, vol.03 his elder brother the Prince of Taiyuan also died. Sima Ji (司马缉;Not to be confused with the Prince of Zhongshan of the same name, who is a second cousin and a grandson of Sima Xun (司马恂), a younger brother of Prince Xian of Anping. son of Gui's elder brother Sima Fu (司马辅) Prince of BohaiSima Fu's fiefdom would be shifted to Taiyuan in 277; the Prince of Taiyuan at the time, Sima Yong, was appointed Prince of Hejian.) was appointed the next Prince of Gaoyang.Jin Shu, vol.37
References
Fang, Xuanling: Book of Jin (Jin Shu).