Maraji (plural of marja) are the supreme legal authority followed by Twelver Shia Muslims, also known as Imamiyyah, around the world. The concept of a Marja al-taqlid () is central to Usuli Shi'a Islam. Marja al-taqlid provides religious interpretations on matters of law and rituals. Ideally, the most just and knowledgeable specialists in the field of Islamic law become recognized as the marja-i taqlid. In practice, this rarely happens and there are several marja al-taqlid whom an individual may choose to emulate.
Clerics who reach the apex of Shi'a theological hierarchy, in centers of learning, become marja-i taqlids. Approximately since 1940, marja-i taqlids are often referred to by their followers with the honorific of Ayatollah al-`Uzma (, where "ayatollah" means "sign of God"). Among the responsibilities of marja-i taqlids are the collection and distribution of religious taxes, such as zakat and khums.