As of the 2022 census, "None" was the largest category of belief in Scotland, chosen by 51.1% of the Scottish population when asked: "What religion, religious denomination or body do you belong to?" This represented a significant increase from the 2011 figure of 36.7%. 38.8% identified as Christian with most of them declaring affiliation with the Church of Scotland (52.5% of Christians; 20.4% of the total population) and the Catholic Church (34.3% of Christians; 13.3% of the total population). The only other religious persuasions with more than 1% affiliation were 'Other Christian' and Muslim at 5.1% and 2.2% of the total population, respectively.

The Church of Scotland, a Presbyterian denomination often known as The Kirk, is recognised in law as the national church of Scotland. It is not an established church and is independent of state control. The Catholic Church is especially important in West Central Scotland and parts of the Highlands. Scotland's third largest church is the Scottish Episcopal Church. There are also multiple smaller Presbyterian churches, all of which either broke away from the Church of Scotland or themselves separated from churches which previously did so. The 2019 Scottish Household survey had a rate of the proportion of adults reporting not belonging to a religion of 56%. The trend of declining religious belief coincided with a sharp decrease since 2009 in the proportion of people who report that they belong to the Church of Scotland, from 34% to 20% of adults.

Other religions have established a presence in Scotland, mainly through immigration and higher birth rates among ethnic minorities. Those with the most adherents in the 2022 census are Islam (2.2%, up from 1.4% in 2011), Hinduism (0.6%), Buddhism (0.3%) and Sikhism (0.2%). Minority faiths include Modern Paganism and the Baháʼí Faith. There are also various organisations which actively promote humanism and secularism. Since 2016, humanists have conducted more weddings in Scotland each year than either the Catholic Church, Church of Scotland, or any other religion and by 2022 the number of humanist marriages outnumbered all religious ceremonies combined.

The statistics from the 2022, 2011 and 2001 censuses are set out below.

Christianity was probably introduced to what is now southern Scotland during the Roman occupation of Britain. It was mainly spread by missionaries from Ireland from the 5th century and is associated with St Ninian, St Kentigern, and St Columba. The Christianity that developed in Ireland and Scotland differed from that led by Rome, particularly over the method of calculating Easter and the form of tonsure, until the Celtic church accepted Roman practices in the mid-7th century. Christianity in Scotland was strongly influenced by monasticism, with abbots being more significant than bishops. In the Norman period, there were a series of reforms resulting in a clearer parochial structure based around local churches; and large numbers of new monastic foundations, which followed continental forms of reformed monasticism, began to predominate. The Scottish church also established its independence from England, developing a clear diocesan structure and becoming a "special daughter of the see of Rome" but continued to lack Scottish leadership in the form of archbishops. In the late Middle Ages the Crown was able to gain greater influence over senior appointments, and two archbishoprics had been established by the end of the 15th century. There was a decline in traditional monastic life but the mendicant orders of friars grew, particularly in the expanding burghs. New saints and cults of devotion also proliferated. Despite problems over the number and quality of clergy after the Black Death in the 14th century, and evidence of heresy in the 15th century, the Church in Scotland remained stable.

During the 16th century, Scotland underwent a Protestant Reformation that created a predominantly Calvinist national kirk, which was strongly Presbyterian in outlook. A confession of faith, rejecting papal jurisdiction and the mass, was adopted by Parliament in 1560. The kirk found it difficult to penetrate the Highlands and Islands, but began a gradual process of conversion and consolidation that, compared with reformations elsewhere, was conducted with relatively little persecution. James VI of Scotland favoured doctrinal Calvinism but supported the bishops. Charles I of England brought in reforms seen by some as a return to papal practice. The result was the Bishop's Wars in 1639–40, ending in virtual independence for Scotland and the establishment of a fully Presbyterian system by the dominant Covenanters. After the Restoration of the Monarchy in 1660, Scotland regained its kirk, but also the bishops. Particularly in the south-west many of the people began to attend illegal field conventicles. Suppression of these assemblies in the 1680s was known as "the Killing Time". After the "Glorious Revolution" in 1688, Presbyterianism was restored.

The Church of Scotland had been created in the Reformation. Then the late 18th century saw the beginnings of its fragmentation around issues of government and patronage, but also reflecting a wider division between the Evangelicals and the Moderate Party. In 1733 the First Secession led to the creation of a series of secessionist churches, and the second in 1761 to the foundation of the independent Relief Church. These churches gained strength in the Evangelical Revival of the later 18th century. Penetration of the Highlands and Islands remained limited. The efforts of the Kirk were supplemented by missionaries of the SSPCK, the Society in Scotland for Propagating Christian Knowledge. Episcopalianism retained supporters, but declined because of its associations with Jacobitism. Beginning in 1834 the "Ten Years' Conflict" ended in a schism from the church, led by Dr Thomas Chalmers, known as the Great Disruption of 1843. Roughly a third of the clergy, mainly from the North and Highlands, formed the separate Free Church of Scotland. The evangelical Free Churches grew rapidly in the Highlands and Islands. In the late 19th century, major debates, between fundamentalist Calvinists and theological liberals, resulted in a further split in the Free Church as the rigid Calvinists broke away to form the Free Presbyterian Church in 1893.

From this point there were moves towards reunion, and most of the Free Church rejoined the Church of Scotland in 1929. The schisms left small denominations including the Free Presbyterians and a remnant that had not merged in 1900 as the Free Church. Catholic Emancipation in 1829 and the influx of large numbers of Irish immigrants led to an expansion of Catholicism, with the restoration of the Church hierarchy in 1878. Episcopalianism also revived in the 19th century; the Episcopal Church in Scotland was organised as an autonomous body in communion with the Church of England in 1804. Other denominations included Baptists, Congregationalists, and Methodists. In the twentieth century, existing Christian denominations were joined by the Brethren and Pentecostal churches. Although some denominations thrived, after World War II there was a steady overall decline in church attendance and resulting church closures in most denominations.