Ismāʿīliy(y)a or Ismāʿīlīs. An aggregation of Muslim groups, notable for esoteric teaching. They emerged historically from disputes following the death of the sixth Shīʿa Imām, Jaʿfar al-Sādiq. The succession should have passed to his eldest son, Ismāʿīl, but he died before his father. Nevertheless, some maintained that the authority had been transmitted to him as the first-born (and beyond him to his son). Others held that the succession should pass to Jaʿfar's eldest surviving son (his third), Mūsā al-Kāzim. The Twelvers (ithnāʿashariyya, majority Shīʿa) chose Mūsā and his successors, while those following Ismāʿīl came to be known as Ismāʿīlīs—and also as Seveners (sabʿiyya), partly for having chosen the Seventh Imām in direct succession, but also because of their belief that prophets always come in cycles of seven. Out of the Ismāʿīlīya there later arose many subsects e.g. Qarmatians, Nizārīs (including Assassins), Mustaʿlīs, Druzes, and Muqannʿah. During the early 10th cent. CE, the Ismāʿīlīs established the powerful and prosperous Fāṭimid dynasty in N. Africa which extended its control, in the 11th cent., to Egypt, Palestine, Syria, Hijāz, Yemen, and Sind. The Fāṭimids were patrons of the arts and sciences and commerce, and they founded the first Islamic universities of al-Azhar and Dār-al-Hikmah in Cairo. The feature which distinguishes Ismāʿīlīs from other Muslim sects is their belief in seven (not five) pillars of faith: belief, purification, prayer, almsgiving, fasting, pilgrimage, and struggle in Allāh's way.

At present the major Ismāʿīlī sect is the Nizārīs, numbering c.20 million, in India, Pakistan, E. Africa, Iran, Syria, and Lebanon. In India, they are known also as Khojas, from the Hindu caste originally converted by a Persian Ismaʿīlī, Ṣadr al-Dīn. Their Imām is the Aga Khān.