Sultan (pronounced [ˈsulˈtˤɑːn]; Arabic: سلطان‎ Sulṭān) is a noble title with several historical meanings. Originally, it was an Arabic language abstract noun meaning 'strength,' 'authority,' 'rulership,' and 'dictatorship,' derived from the masdar سلطة sulṭah, meaning 'authority' or 'power.' Later, it came to be used as the title of certain rulers who claimed almost full sovereignty in practical terms (i.e. the lack of dependence on any higher ruler), without claiming the overall caliphate, or it was used to refer to a powerful governor of a province within the caliphate.

The dynasty and lands ruled by a sultan are referred to as a sultanate (Arabic: سلطنة‎).

The title carries moral weight and religious authority, in the Qur'an. The sultan, however, is not a religious teacher himself, and in constitutional monarchies, the sultanship can be reduced to a more limited role.

Sultan was the usual title of rulers of Seljuk and Ottoman Turks and Ayyubid and Mamluk rulers in Egypt. The religious validation of the title was illustrated by the fact that the shadow Caliph in Cairo bestowed the title sultan on Murad I, the third ruler of the emerging Ottoman Empire in 1383; its earlier sovereigns had been beys or emirs, a lower rank in the orders of protocol.