Ahmadiyya (Arabic: أحمدية‎;Urdu: احمدِیہ) is an Islamic reformist movement founded in British India near the end of the 19th century, originating with the life and teachings of Mirza Ghulam Ahmad (1835–1908), who claimed to have fulfilled the prophecies about the world reformer of the end times, who was to herald the Eschaton as predicted in the traditions of various world religions and bring about the final triumph of Islam as per Islamic prophecy. He claimed that he was the Mujaddid (divine reformer) of the 14th Islamic century, the promised Messiah and Mahdi awaited by Muslims. The adherents of the Ahmadiyya movement are referred to as Ahmadis or Ahmadi Muslims.

Ahmadi thought emphasizes the belief that Islam is the final dispensation for humanity as revealed to Muhammad and the necessity of restoring to it its true essence and pristine form, which had been lost through the centuries. Thus, Ahmadis view themselves as leading the revival and peaceful propagation of Islam. The Ahmadis were among the earliest Muslim communities to arrive in Britain and other Western countries.