Located in Southfields, London near King George's Park and Southfields train station, the Fazl Mosque, also known as the London Mosque, was inaugurated on 23 October 1926. This mosque was the first Ahmadiyya mosque built in Britain and the first purpose-built mosque in London.

The majority of the funding for the Fazl Mosque was contributed by Ahmadi women in India, who donated their jewellery and possessions to construct the first purpose-built mosque in London. The foundation stone was laid in 1924 by Hazrat Mirza Basheer-ud-Din Mahmood Ahmad, who was representing Islam at The Conference of Living Religions being held at The Imperial Institute in South Kensington. The foundation ceremony was attended by 200 guests.

The mosque, which can accommodate 150 worshippers, was constructed in September 1925 and completed ten months later. His Holiness Hazrat Hadrat Mirza Basheeruddeen Mahmood Ahmad named it the 'Fazl Mosque', with 'Fazl' meaning Grace.

On 23 October 1926, the mosque was officially opened, with 600 distinguished guests representing several countries, local MPs, and other dignitaries attending the ceremony, which was widely reported in the press.

Today, the Fazl Mosque is the international headquarters of the Ahmadiyya Muslim Community, and it is the residence of the community’s worldwide leader, His Holiness Hazrat Mirza Masroor Ahmad, who is the fifth leader of the community. The community has numerous mosques and centres throughout the United Kingdom, with members from various backgrounds and professions. The community's guiding principle is 'Love for All, Hatred for None.'