Zaydism (Arabic: الزَّيْدِيَّة, romanized: az-Zaydiyya) is one of the three main branches [1] of Shia Islam that emerged in the eighth century following Zayd ibn Ali's unsuccessful rebellion against the Umayyad Caliphate. [2] Zaydism is typically considered to be a branch of Shia Islam that comes closest to the Sunni, although the "classical" form of Zaydism (usually referred to ...