Scottish religion in the eighteenth century includes all forms of religious organisation and belief in Scotland in the eighteenth century. This period saw the beginnings of a fragmentation of the Church of Scotland that had been created in the Reformation and established on a fully Presbyterian basis after the Glorious Revolution. These fractures were prompted by issues of government and patronage, but reflected a wider division between the Evangelicals and the Moderate Party. The legal right of lay patrons to present clergymen of their choice to local ecclesiastical livings led to minor schisms from the church. The first in 1733, known as the First Secession and headed by figures including Ebenezer Erskine, led to the creation of a series of secessionist churches. The second in 1761 led to the foundation of the independent Relief Church.
In 1743, the Cameronians established themselves as the Reformed Presbyterian Church, remaining largely separate from religious and political debate. Of independent churches from England that were established in the seventeenth century only the Quakers managed to endure in to the eighteenth century. Baptist chapels were re-established in the middle of the century and, although Scotland initially appeared fertile ground for Methodism, it failed to expand as quickly as elsewhere in the Great Britain and Ireland. A number of minor Scottish sects developed, such as the Bereans, Buchanites, Daleites and Glassites.
Episcopalianism had retained supporters through the Wars of the Three Kingdoms and changes of regime in the seventeenth century. Since most Episcopalians gave their support to the Jacobite rebellions in the first half of the early eighteenth century, they suffered a decline in fortunes. The remoteness of the Highlands and the lack of a Gaelic-speaking clergy undermined the missionary efforts of the established church. The later eighteenth century saw some success, owing to the efforts of the SSPCK missionaries and to the disruption of traditional society. Catholicism had been reduced to the fringes of the country, particularly the Gaelic-speaking areas of the Highlands and Islands. Conditions grew worse for Catholics after the Jacobite rebellions and Catholicism was reduced to little more than a poorly run mission. There was Evangelical Revival from the 1730s, reaching its peak at the Cambuslang Wark in 1742. The movement benefited the secessionist churches who gained recruits.
The Kirk had considerable control over the lives of the people, with a major role in the Poor Law and schools and over the morals of the population. Strict Sabbatarianism was vital to Presbyterianism. The sermon was seen as central and the only participation by the congregation the singing of the psalms. Communion was the central occasion of the church, conducted infrequently, at most once a year, often taking a week of festivals as part of a communion season. In the second half of the century there were a series of reforms of church music connected to a choir movement. Episcopalians installed organs and hired musicians, following the practice in English parish churches. Catholic worship was deliberately low key, with musical accompaniment prohibited.