The Clapham Sect was an Anglican Evangelical group centred around John Venn (1793-1813), rector of the Holy Trinity Church, Clapham. Venn had become curate of Clapham. He met the banker, John Thornton, a man who was very interested in the subject of social reform. According to Leonard W. Cowie: "Clapham was already becoming an evangelical centre, and there Venn came under the influence of John Thornton, the banker, who bought the advowson of Clapham." In 1763 Venn published The Complete Duty of Man.

The group surrounding John Venn, who were nicknamed the Saints, included William Wilberforce, Hannah More, Granville Sharp, Henry Thornton, Zachary Macaulay, James Stephen, Edward James Eliot, Thomas Gisbourne, John Shore and Charles Grant. Most members of the group were active in the campaign against the slave trade. John Wolffe, Wilberforce's biographer, has argued: "The 1790s and 1800s marked the heyday of what was later labelled the Clapham Sect, the group of wealthy evangelicals around Wilberforce and Henry Thornton whose other notable members included Edward Eliot, Charles Grant, Zachary Macaulay, John Shore (Lord Teignmouth), and James Stephen.... This circle of friends was of great importance to Wilberforce in providing emotional and practical support for the ongoing anti-slave-trade campaign."