An Najaf (än näˈjäf) [key], city (1987 pop. 309,010), S central Iraq, on a lake near the Euphrates River. The city, one of Shi'a Islam's holiest, is also called Mashad Ali, after the tomb (in a mosque) of Ali, son-in-law of Muhammad the Prophet. The tomb is an object of pilgrimage by Shiite Muslims and a starting point for the pilgrimage to Mecca. An Najaf also is an important Shiite theological and educational center; Iraq's senior Shiite clergy reside there. The city was the center of fighting between U.S. forces and Shiite insurgents in 2004.