Musta'li Isma'ilism (Arabic: المستعلية, romanized: al-Mustaʿliyya) is a branch of Isma'ilism named for their acceptance of al-Musta'li as the legitimate ninth Fatimid caliph and legitimate successor to his father, al-Mustansir Billah (r. 1036–1094/1095). The Nizari the other living branch of Ismailism, led by Aga Khan V believe the ninth caliph was al-Musta'li's elder brother, Nizar.

The Musta'li originated in Fatimid-ruled Egypt, later moved its religious center to Yemen, and gained a foothold in 11th-century Western India through missionaries.

Historically, there was a distinction between the Tayyibi and the Hafizi Musta'lis, the former recognising Abu'l-Qasim al-Tayyib as the legitimate heir of the Imamate after al-Amir bi-Ahkam Allah and the latter following al-Hafiz, who was enthroned as caliph. The Hafizi view lost all support following the downfall of the Fatimid Caliphate: later Musta'lis are all Tayyibi.

Syedna Mohammed Burhanuddin was the 52nd Da'i al-Mutlaq of the Dawoodi Bohra community. After he died in 2014 Syedna Mufaddal Saifuddin succeeded him, as the 53rd Da'i al-Mutlaq of The Dawoodi Bohra community.

According to Musta'lī tradition, after the death of al-Amir bi-Ahkam Allah, his infant son, Abu'l-Qasim al-Tayyib, about two years old, was protected by Arwa al-Sulayhi who died in 1138, wife of the chief Fatimid Da'i of Yemen. She had been promoted to the post of Hujjat al-Islam long before by al-Mustansir Billah when her husband died and ran the Fatimid dawah from Yemen in the name of Imam Abu'l-Qasim al-Tayyib. During her leadership Abu'l-Qasim al-Tayyib went into occultation so she instituted the office of Da'i al-Mutlaq. Zoeb bin Moosa was first to be instituted to this office and the line of Tayyibi Da'is that began in 1132. Arwa al-Sulayhi was the Hujjah in Yemen from the time of Imam Al-Mustansir Billah. She appointed the Da'i in Yemen to run religious affairs. Isma'ili missionaries Ahmed and Abdullah (in about 1067 AD (460 AH)) were also sent to India in that time. They sent Syedi Nuruddin to Dongaon to look after southern part and Syedi Fakhruddin to East Rajasthan, India.

Imams 11–21 were caliphs who ruled the Fatimid Caliphate.^{[citation needed]}

The imams from Muhammad ibn Isma'il onward were occulted by the Musta'li; their names as listed by Dawoodi Bohra religious books are listed above.

Arwa al-Sulayhi was the Hujjah from the time of Imam Mustansir. She appointed Dai in Yemen to run religious affair. Ismaili missionaries Ahmed and Abdullah (in about 1067 AD (460 AH)) were sent to India in that time. According to Fatimid tradition, after the death of Al-Amir bi-Ahkami'l-Lah, Arwa al-Sulayhi instituted the Da'i al-Mutlaq in place of Dai to run the independent dawah from Yemen in the name of Imam Tayyib. The Dais are appointed one after other in the same philosophy of nass (nomination by predecessor) as done by earlier imams. It is believed that God's representative cannot die before appointing his true successor. This is being followed from the time of 3rd Imam Ali al-Sajjad, the strong army of Yazid also could not think of killing him, although they did not spare even a child of six months, Ali al-Asghar ibn Husayn.