Mujaddid () in Islam is a reformer who is given the task of removing errors that have occurred among Muslims. Their job is to show people the great religious truths which the Muslim community will be asked to face. According to the popular Muslim tradition, it refers to a person who appears at the turn of every century of the Islamic calendar to revive Islam, cleansing it of extraneous elements and restoring it to its pristine purity. In contemporary times, a mujaddid is looked upon as the greatest Muslim of a century.