Mirza Basheer-ud-Din Mahmood Ahmad (; 12 January 1889 – 8 November 1965) was the second caliph (, khalīfatul masīh al-thāni), leader of the worldwide Ahmadiyya Muslim Community and the eldest son of Mirza Ghulam Ahmad from his second wife, Nusrat Jahan Begum. He was elected as the second successor of Mirza Ghulam Ahmad on 14 March 1914 at the age of 25, the day after the death of his predecessor Hakim Nur-ud-Din.
Mahmood Ahmad's election as second caliph saw a secession within the movement in which a party refrained from pledging allegiance to him on account of certain differences over succession and theology; and possibly owing to a clash of personalities. He led the Ahmadiyya Muslim Community for over half a century and is known for establishing virtually the entire organisational structure of the Community (including five Auxiliary Organisations), improvement of its administration, formally establishing the Majlis al-Shura (Consultative Council), consolidating and formalising the system of financial contributions of the Community and directing extensive missionary activity beyond the Indian subcontinent. He is also known for his Tafsīr-e-Kabīr, a ten-volume exegesis of the Qur'an. A renowned orator, Mahmood Ahmad was also an active political figure especially in pre-independence India. He was also one of the founding members and the first president of the All India Kashmir Committee set up for the establishment of the civil rights of Kashmiri Muslims. Following the Partition of India and the creation of Pakistan in 1947, he carefully oversaw the safe migration of Ahmadis from Qadian to the newly found state, eventually building a town on a tract of arid and mountainous land bought by the Community in 1948 which now became its new headquarters and was named Rabwah. A 26 volume compilation of his works called Anwārul Uloom contains over 800 writings and lectures (excluding the many thousands of sermons). Mahmood Ahmad is regarded by the Ahmadiyya Muslim Community as the Musleh Ma'ood (Promised Reformer) and the "Promised Son" that Ghulam Ahmad foretold God would bestow upon him.
Early life
Mirza Basheer-ud-Din Mahmood was born to Ghulam Ahmad and Nusrat Jahan Begum on 12 January 1889 in Qadian, the same year in which Ghulam Ahmad established the Ahmadiyya Movement by accepting allegiance from his disciples. Due to chronic illness Mahmood Ahmad was unable to attend to secondary education. During his youth, he remained an active member in the service of the Movement by founding a journal entitled Tash'heezul Az'haan and accompanied his father on many of his journeys. On 26 May 1908, Ghulam Ahmad died in Lahore when Mahmood Ahmad was 19 years old. The next day on 27 May 1908, he gave the pledged allegiance to Hakeem Noor-ud-Din, who had been chosen to succeed Ghulam Ahmad. After the passing of his father, Mahmood Ahmad continued to study the Quran, Sahih Bukhari, the Masnavi and some medicine under the tutelage of Noor-ud-Din, with whom he developed a close friendship. Noor-ud-Din would eventually become one of the leading influences in Mahmood's life. He also began writing articles for various periodicals for the Community and would often engage himself in theological debates with various scholars of the Community. Mahmood Ahmad visited Egypt and Arabia in September 1912 during the course of which he performed the Hajj pilgrimage. Upon his return to Qadian in June 1913, he started a newspaper, titled Al-Fazl. Within the Community, the newspaper serves as a vehicle for the moral upbringing of its members, Islamic education and preservation of the Community's history.