Zaydism is a branch of Shia Islam that originated in the 8th century. It is named after Zayd ibn Ali, the grandson of Husayn ibn Ali, who led a revolt against the Umayyad caliphate. Zaydism emphasizes the importance of social justice and the right to revolt against unjust rulers, distinguishing it from other Shia sects. Zaydism is primarily practiced in Yemen, where it has played a significant role in the country's history and politics. Zaydi Muslims believe in the leadership of the Imams, who are seen as divinely appointed leaders. Unlike other Shia groups, Zaydism does not require the belief in a specific line of Imams, allowing for a more flexible interpretation of leadership.