London has centres of worship for a multitude of faiths. According to the 2011 Census, the largest religious groupings are Christians (48.4 per cent), followed by those of no religion (20.7 per cent), no response (8.5 per cent), Muslims (12.4 per cent), Hindus (5.0 per cent), Jews (1.8 per cent), Sikhs (1.5 per cent), Buddhists (1.0 per cent) and other (0.6 per cent).
London is significantly more religious than England or the UK as a whole, in part as a reflection of its racial and cultural diversity. In 2001, the numbers were respectively Christians (58.2 per cent), followed by those of no religion (15.8 per cent), no response (8.7 per cent), Muslims (8.5 per cent), Hindus (4.1 per cent), Jews (2.1 per cent), Sikhs (1.5 per cent), Buddhists (0.8 per cent) and other (0.5 per cent).
Historically, London has been predominantly Christian. This is clear from the large number of churches around the area, particularly in the City of London, which alone contains around 50 churches. Anglicanism is the primary denomination, and the Archbishop of Canterbury's main residence is actually at Lambeth Palace. Most parts of London north of the Thames and west of the River Lee are within the diocese of London under the Bishop of London at the famous St Paul's Cathedral in the City, parishes east of the River Lee are within the Diocese of Chelmsford, whilst most parts south of the river are administered from Southwark Cathedral as the diocese of Southwark. Important national and royal ceremonies are divided between St Paul's and Westminster Abbey.
The pre-eminent Catholic cathedral in England and Wales is Westminster Cathedral, from where the Archbishop of Westminster leads the English and Welsh Catholic church. Other Christian denominations also have headquarters in the city, including the United Reformed Church, the Salvation Army and the Quakers, and immigrant communities have established their own denominations or dioceses (e.g. Greek Orthodoxy). Evangelical churches are also present in the city.
Islam is London's second largest religion. 38% of England's Muslims live in London, where they represent 12.4% of the population. There were 1,012,823 Muslims reported in the 2011 census in the Greater London area.
London's first Mosque was established by Mohamad Dollie in 1895, modern day Camden. The Mosque is a focus of a forthcoming documentary with Muslim History Tours. The East London Mosque is the largest Muslim centre in Europe. London Central Mosque is a well-known landmark on the edge of Regent's Park, and there are many other mosques in the city. However, another landmark was set when Baitul Futuh Mosque was constructed in 2003 by the Ahmadiyya Muslim Community, being the largest mosque in Western Europe.
In 2013, it was reported there were 13,400 Muslim-owned businesses in London, creating more than 70,000 jobs and representing just over 33 per cent of Small to Medium Enterprises in London. 
Over half of the UK's Hindu population live in London, where they make up 5% Every borough has a significant Hindu population and as per the 2011 census, the London borough of Harrow has the largest concentration of Hindus at 25%.
The Hindu temple at Neasden was the largest temple of Hinduism in Europe, until the opening of the Shri Venkateswara (Balaji) Temple in Tividale in 2006. Other temples are located in nearby Wembley, Harrow and Willesden, as well as Wimbledon and Newham in South and East London.
Over two-thirds of British Jews live in London, which ranks thirteenth in the world as a Jewish population centre. There are significant Jewish communities in parts of north London such as Stamford Hill and Golders Green. There are currently two eruvin in London; one that covers Hendon, Golders Green, and Hampstead Garden Suburb, and another in Edgware. There are two more planned eruvin; one in Stanmore, and one covering Elstree/Borehamwood.
The first written record of Jewish settlement in London dates from 1070, although Jews may have lived there since Roman times. Bevis Marks Synagogue built in 1701 in the city of London is the oldest synagogue in the United Kingdom still in use. In 1899, a map was published showing by colour the proportion of the Jewish population to other residents of East London, street by street. It illustrates clearly the predominantly Jewish population at the time of the areas of Whitechapel, Spitalfields and Mile End in particular.
Roughly in one in five Londoners have no religion, and much of London's civic life and civil society is secular in the sense that it has no religious character.
To the extent that non-religious movements have actively organised in the UK, many organise nationally from London. The non-religious humanist movement in the UK largely began in London in the 19th century with the foundation of various "ethical churches" and "ethical societies". Over time, these groups came to form the basis of non-religious charities in the UK: Conway Hall, based in the former South Place Ethical Society in Holborn, and Humanists UK, which was formed by the merger of the UK's remaining ethical societies. Of Humanists UK's London chapters, the largest is the Central London Humanist Group, which frequently meets at Conway Hall.
The 19th-century non-religious congregational model of the ethical churches still persists to some extent. The non-religious Sunday Assembly movement began in London in 2013, since becoming a global feel-good movement for non-religious people who want to sing songs and celebrate life. Unitarian groups in Islington and Hackney also now organise under the umbrella of the "New Unity" church, which bills itself as "a non-religious church" and "a radically inclusive church: people of all backgrounds, ages, sexualities, and abilities."