Twelver (Arabic: اثنا عشرية, translit. Athnā‘ashariyyah or Ithnā‘ashariyyah; Persian: شیعه دوازدهامامی, pronounced [ʃiːʔe-je dævɑzdæh emɑmiː]) or Imamiyyah (Arabic: إمامية) is the largest branch of Shia Islam. The term Twelver refers to its adherents' belief in twelve divinely ordained leaders, known as the Twelve Imams, and their belief that the last Imam, Muhammad al-Mahdi, lives in occultation and will reappear as the promised Mahdi. According to Shia tradition, the Mahdi's tenure will coincide with the Second Coming of Jesus Christ (Isa), who is to assist the Mahdi against the Masih ad-Dajjal (literally, the "false Messiah" or Antichrist).
Twelvers believe that the Twelve Imams are the spiritual and political successors to the Islamic prophet Muhammad. According to the theology of Twelvers, the Twelve Imams are exemplary human individuals who not only rule over the community with justice, but are also able to preserve and interpret sharia and the esoteric meaning of the Quran. The words and deeds (Sunnah) of Muhammad and the Imams are a guide and model for the community to follow; as a result, Muhammad and the Imams must be free from error and sin, a doctrine known as Ismah or infallibility, and must be chosen by divine decree, or nass, through Muhammad.
The largest branch of Shia Islam is the Twelver Shia, with about 85% of all Shias that can be estimated approximately between 148 and 296 million Twelver Shias.
Twelvers make majorities among Muslims in Iran, Azerbaijan, Iraq, Bahrain. Also, they make significant minorities in India, Pakistan, Afghanistan, Saudi Arabia, Yemen, Bangladesh, Kuwait, Oman, UAE, Qatar, Nigeria, Chad, and Tanzania.
Iran is the only country with state religion as (Twelver) Shia Islam.
Twelvers share many tenets of Shia with related sects, such as the belief in Imams, but the Ismaili Shias believe in a different number of Imams and, for the most part, a different path of succession regarding the Imamate. They also differ in the role and overall definition of an Imam. Twelvers are also distinguished from Ismailis by their belief in Muhammad's status as the "Seal of the Prophets" (Khatam an-Nabiyyin), in rejecting the possibility of abrogation of Sharia laws, and in considering both esoteric and exoteric aspects of the Quran. Alevis in Turkey and Albania, and Alawites in Syria and Lebanon, share belief in the Twelve Imams with Twelvers, but their theological doctrines are remarkably different.