Mustā‘lī Ismāʿīlī or Mustā‘lī is a sect of Ismā'īlī Shia Islam, so named for their acceptance of Al-Musta'li as the nineteenth Fatimid caliph and legitimate successor to his father, al-Mustansir. In contrast, the Nizāriyya Muslims—presently headed by the Aga Khan—believe the rightful nineteenth caliph was Musta'lī's elder brother, Nizār. The Mustaʿlī sect originated in Egypt, later moved its religious center to Yemen, and gained a foothold in India through missionaries of the 11th century.