William Smith was a leading independent British politician, sitting as Member of Parliament (MP) for more than one constituency. He was an English Dissenter and was instrumental in bringing political rights to that religious minority. He was a friend and close associate of William Wilberforce and a member of the Clapham Sect of social reformers, and was in the forefront of many of their campaigns for social justice, prison reform and philanthropic endeavour, most notably the abolition of slavery. He was the grandfather of pioneer nurse and statistician Florence Nightingale and educationalist Barbara Bodichon, a founder of Girton College, Cambridge.

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.