Mǎ Sù (馬謖), courtesy name Yòucháng (幼常), was a general for Liu Biao of the Han dynasty in China until the death of Liu Biao in 199 AD. Zhuge Liang saw his skills as a sorcerer, archer and general and invited him to join Liu Bei's army of Shu. He accepted.

He was very useful against the forces of the south like Nanman and Wu. On the first Northern Campaign, he was ordered by Zhuge Liang to guard a strategic position, Jiētīng (街亭). However, he failed to obey orders and advice from his deputy generals, and camped onto the mountain, causing his defeat, and eventually the retreat of the Shu army. In 219, Zhuge Liang had him beheaded, as he had signed an edict earlier, promising his life if he failed in his mission.

Jiang Wan arrived and tried to stop Zhuge Liang, but his mind was set. Later, Zhuge Liang cried, and when asked, he replied that he was merely thinking about the words of the late Liu Bei, who had told him, on his deathbed, that Ma Su was untrusty and not able for important missions.