Sima Guang 司馬光 (1019–1086), style name Junshi 君實, was a writer and politician during the Song Dynasty 宋 (960–1279). By the Three Kingdoms enthusiasts he is probably best remembered as the compiler of the 294 juan 卷 long chronological historywork Comprehensive Mirror for Aid in Government (Zizhi tongjian 資治通鑒).
Sima Guang had always been interested in history but was repelled by the structure of traditional historiography which made an access to events and their circumstances very cubersome, especially in the official dynastic histories that are written in a biographic-thematic style (jizhuanti 紀傳體). He therefore decided to write history by himself.