The Fazl Mosque also known as The London Mosque, is the first purpose-built mosque in London, England. It was opened on 23 October 1926 in Southfields, Wandsworth. At a cost of £6,223, the construction of the mosque and the purchase of the land on which it stands, was financed by the donations of Ahmadi Muslim women in Qadian, Punjab, British India, with support from the British Muslim convert Khalid Sheldrake. Between 1984 and 2019 the Fazl Mosque was the residence of the caliphs of the Ahmadiyya Muslim Community, and therefore its de facto international headquarters. The administrative headquarters now lies at the site of the Islamabad, Tilford.

Southfields is a district of inner London located within the London Borough of Wandsworth, England, 5.6 miles (9 km) south-west of Charing Cross. Southfields is mainly residential, historically a part of Wandsworth itself, and is divided between the SW18 and SW19 postcode areas.