Ghiyath ad-Din Muhammad Tapar (died 1118) was a son of Seljuk Sultan Malik Shah I. He succeeded his nephew, Malik Shah II, as Seljuk Sultan in Baghdad, and thus was theoretically the head of the dynasty, although his brother Ahmed Sanjar in Khorasan probably held more practical power. Muhammad I (probably) allied himself with Radwan of Aleppo in the Battle of Mosul against Kilij Arslan I, the sultan of Rüm, in 1107, where Kilij Arslan was defeated and later killed. Muhammad I died in 1118 and was succeeded by Mahmud II, although after Muhammad's death Sanjar was clearly the chief power in the Seljuk realms.