Unitarianism, a small religious body committed to a liberal religious faith without dogma or creeds, has its roots in the radical wing of the Protestant Reformation and the eighteenth-century Enlightenment. Because they rejected the doctrine of the Trinity, Unitarians were generally regarded as outside the borders of Christian orthodoxy.

A Unitarian Christian congregation was formed in Adelaide in 1855 and a church opened in Wakefield Street in 1857, with a branch church founded in 1865 at Shady Grove, near Hahndorf in the Adelaide Hills. For 34 years the intellectual preaching of JC Woods, the first minister of the Adelaide church, appealed to liberal-minded, educated and generally well-to-do people.

During the nineteenth century the Unitarians, although numerically small, had a more visible presence in Adelaide than elsewhere in Australia. The congregation included such prominent politicians and business leaders as Edward Morgan, Sir Henry Ayers and Alfred Muller Simpson. Other Unitarians, such as John Howard Clark and Robert Kay, were active in the cause of popular education. Catherine Helen Spence joined the church in 1856, later preaching there occasionally. In the twentieth century the fortunes of the congregation fluctuated, largely depending on the resident minister. In 1973 the Wakefield Street church was demolished, having been replaced by a modern meeting house at suburban Norwood.

While other denominations have liberalised their theology, Unitarians have moved in a still more radical direction. They are less likely than previously to see themselves as liberal Christians, emphasising instead the importance of free inquiry, tolerance of religious differences and individual spiritual exploration, drawing on the insights of all religions. The Adelaide church removed ‘Christian’ from its name in 1977. At the 2011 census there were about 400 Unitarian adherents in South Australia.