Mirza Tahir Ahmad was the fourth caliph and the head of the worldwide Ahmadiyya Muslim Community. He was elected as the fourth successor of the founder of the community, Mirza Ghulam Ahmad. He was elected on 10 June 1982, the day after the death of his predecessor, Mirza Nasir Ahmad.

The Ahmadiyya Caliphate is a non-political caliphate established on May 27, 1908, following the death of Mirza Ghulam Ahmad, the founder of the Ahmadiyya Muslim Community, who claimed to be a Prophet, a Messenger, the promised Messiah and Mahdi, the expected redeemer awaited by Muslims. It is believed by Ahmadis to be the re-establishment of the Rashidun Caliphate that commenced following the death of the Islamic prophet Muhammad. The caliphs are entitled Khalīfatul Masīh, sometimes simply referred to as Khalifa. The caliph is the elected spiritual and organizational leader of the worldwide Ahmadiyya Muslim Community and is the successor of Ghulam Ahmad. He is believed by the Community to be divinely ordained and is also referred to by its members as Amir al-Mu'minin and Imam Jama'at. The 5th and current Caliph of the Messiah of the Ahmadiyya Community is Mirza Masroor Ahmad.