Sima Guang (司馬光; 1019–1086) was a Chinese historian, scholar, and high chancellor of the Song Dynasty, jinshi(進士 "metropolitan graduate") 1038.

Sima Guang was born in 1019 in present-day Yuncheng, Shanxi to a wealthy family, and obtained early success as a scholar and officer. When he was barely twenty, he passed the Imperial examination with the highest rank of jìnshì (進士 "metropolitan graduate"), and spent the next several years in official positions.

Such loyalty is notable, especially since Sima was a leader of the conservative faction at court, resolutely opposed to the reformist policies of Chancellor Wang Anshi(王安石). Sima presented increasingly critical memorials to the throne until 1070, when he refused further appointment and withdrew from court. In 1071, he took up residence in Luoyang(洛陽). Indeed, though the historian and the emperor continued to disagree on policies, Sima's enforced retirement proved essential for him to fully complete his chronological history, Zizhi Tongjian(資治通鑑).