branch of Shia Islam
The Zaidiyyah (Arabic: الزيدية) are a Shia Muslim sect. They are different from the usual Shia Islam. This is because of the argument over the who the 5th Imam, or religious leader, is. They believe the 5th Imam was Zaid ibn Ali while usual Shia Muslims believe that his brother, Muhammad, was the 5th Imam.
Today, they make up 40% of the population of Yemen. The president of Yemen is also Zaidi.