al-Mahdi al-Husayn (987 - 1013) was an imam of the Zaidi state in Yemen who ruled in the years 1003–1013, in rivalry with another imam. Like most of the medieval Yemenite imams he was a member of the Rassid line. His genealogy was as follows: Al-Husayn bin Imam al-Qasim bin Ali bin Abdullah bin Muhammad bin Imam al-Qasim al-Rassi bin Ibrahim Tabataba bin Isma'il al-Dibaj bin Ibrahim bin al-Hasan al-Ridha bin Imam al-Hasan bin Imam Ali bin Abi Talib.