Ma Su (190–228), courtesy name Youchang, was a military general and strategist of the state of Shu Han in the Three Kingdoms period of China. 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. He was a younger brother of Ma Liang.