The Clapham Sect, or Clapham Saints, were a group of social reformers associated with Holy Trinity Clapham in the period from the 1780s to the 1840s. Despite the label "sect", most members remained in the established Church of England, which was highly interwoven with offices of state. However, its successors were in many cases outside of the established Anglican Church.

The Holy Trinity Church is an Anglican church located in Clapham, London. Completed in 1776, it was the base for the so-called Clapham Sect who worshipped there. It is located on the north side of Clapham Common and is a Grade II* listed building.