Christianity has been the largest religion by number of adherents since the Early Middle Ages: it was introduced under the ancient Romans, developing as Celtic Christianity.
According to tradition, Christianity arrived in the 1st or 2nd century.
The most popular form is Anglicanism (known as Episcopalism in Scotland).
Dating from the 16th-century Reformation, it regards itself as both Catholic and Reformed.
The Head of the Church is the monarch of the United Kingdom, as the Supreme Governor.
It has the status of established church in England.
There are just over 26 million adherents to Anglicanism in Britain today, although only around one million regularly attend services.
The second largest Christian practice is the Latin Rite of the Roman Catholic Church, which traces its history to the 6th century with Augustine's mission and was the main religion for around a thousand years.
There are over 5 million adherents today, 4.5 million in England and Wales and 750,000 in Scotland, although fewer than a million Catholics regularly attend mass.

The Church of Scotland, a form of Protestantism with a Presbyterian system of ecclesiastical polity, is the third most numerous on the island with around 2.1 million members.
Introduced in Scotland by clergyman John Knox, it has the status of national church in Scotland.
The monarch of the United Kingdom is represented by a Lord High Commissioner.
Methodism is the fourth largest and grew out of Anglicanism through John Wesley.
It gained popularity in the old mill towns of Lancashire and Yorkshire, also amongst tin miners in Cornwall.
The Presbyterian Church of Wales, which follows Calvinistic Methodism, is the largest denomination in Wales.
There are other non-conformist minorities, such as Baptists, Quakers, the United Reformed Church (a union of Congregationalists and English Presbyterians), Unitarians.
The first patron saint of Great Britain was Saint Alban.
He was the first Christian martyr dating from the Romano-British period, condemned to death for his faith and sacrificed to the pagan gods.
In more recent times, some have suggested the adoption of St Aidan as another patron saint of Britain.
From Ireland, he worked at Iona amongst the Dál Riata and then Lindisfarne where he restored Christianity to Northumbria.

The three constituent countries of the United Kingdom have patron saints: Saint George and Saint Andrew are represented in the flags of England and Scotland respectively.
These two flags combined to form the basis of the Great Britain royal flag of 1604.
Saint David is the patron saint of Wales.
There are many other British saints.
Some of the best known are Cuthbert, Columba, Patrick, Margaret, Edward the Confessor, Mungo, Thomas More, Petroc, Bede, and Thomas Becket.

Numerous other religions are practised.
Jews have inhabited Britain since 1070.
Jews were expelled from England in 1290 but permitted to return in 1656.
There were also Jewish migrations from Lithuania.
The 2001 census recorded that Islam had around 1.5 million adherents.
More than 1 million people practise either Hinduism, Sikhism, or Buddhism–religions introduced from the Indian subcontinent and Southeast Asia.
Christianity has been the largest religion by number of adherents since the Early Middle Ages: it was introduced under the ancient Romans, developing as Celtic Christianity. According to tradition, Christianity arrived in the 1st or 2nd century. The most popular form is Anglicanism (known as Episcopalism in Scotland). Dating from the 16th-century Reformation, it regards itself as both Catholic and Reformed. The Head of the Church is the monarch of the United Kingdom, as the Supreme Governor. It has the status of established church in England. There are just over 26 million adherents to Anglicanism in Britain today, although only around one million regularly attend services. The second largest Christian practice is the Latin Rite of the Roman Catholic Church, which traces its history to the 6th century with Augustine's mission and was the main religion for around a thousand years. There are over 5 million adherents today, 4.5 million in England and Wales and 750,000 in Scotland, although fewer than a million Catholics regularly attend mass.
The Church of Scotland, a form of Protestantism with a Presbyterian system of ecclesiastical polity, is the third most numerous on the island with around 2.1 million members. Introduced in Scotland by clergyman John Knox, it has the status of national church in Scotland. The monarch of the United Kingdom is represented by a Lord High Commissioner. Methodism is the fourth largest and grew out of Anglicanism through John Wesley. It gained popularity in the old mill towns of Lancashire and Yorkshire, also amongst tin miners in Cornwall. The Presbyterian Church of Wales, which follows Calvinistic Methodism, is the largest denomination in Wales. There are other non-conformist minorities, such as Baptists, Quakers, the United Reformed Church (a union of Congregationalists and English Presbyterians), Unitarians. The first patron saint of Great Britain was Saint Alban. He was the first Christian martyr dating from the Romano-British period, condemned to death for his faith and sacrificed to the pagan gods. In more recent times, some have suggested the adoption of St Aidan as another patron saint of Britain. From Ireland, he worked at Iona amongst the Dál Riata and then Lindisfarne where he restored Christianity to Northumbria.
The three constituent countries of the United Kingdom have patron saints: Saint George and Saint Andrew are represented in the flags of England and Scotland respectively. These two flags combined to form the basis of the Great Britain royal flag of 1604. Saint David is the patron saint of Wales. There are many other British saints. Some of the best known are Cuthbert, Columba, Patrick, Margaret, Edward the Confessor, Mungo, Thomas More, Petroc, Bede, and Thomas Becket.
Numerous other religions are practised. Jews have inhabited Britain since 1070. Jews were expelled from England in 1290 but permitted to return in 1656. There were also Jewish migrations from Lithuania. The 2001 census recorded that Islam had around 1.5 million adherents. More than 1 million people practise either Hinduism, Sikhism, or Buddhism–religions introduced from the Indian subcontinent and Southeast Asia.
Great Britain