Ma Su (190–228), courtesy name Youchang, was a military general and strategist of the state of Shu Han in the Three Kingdoms period. He was a younger brother of Ma Liang. Ma Su had conspicuous talent in military theories and was admired by the Shu chancellor Zhuge Liang. However, a tactical blunder by Ma Su at the Battle of Jieting resulted in Shu being dealt a huge defeat by Zhang He, a general of the rival state of Wei.Much dramatization shrouds the death of Ma Su.