William Smith (1756–1835) 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 maternal grandfather of pioneer nurse and statistician Florence Nightingale.
William Smith was born on 22 September 1756 at Clapham (then a village to the south of London), the only son of Samuel Smith by Martha, daughter of William Adams of London. Brought up by parents who worshipped at an Independent chapel, he was educated at the dissenting academy at Daventry until 1772, where he began to come under the influence of Unitarians. He went into the family grocery business and by 1777 had become a partner. Smith had a long career as a social and political reformer, joining the Society for Constitutional Information in 1782.
On 12 September 1781 he married Frances Coape (1758 – 1840), daughter of John and Hannah Coape, both Dissenters. Their daughter, Frances Smith, married William Nightingale and was the mother of Florence Nightingale. According to Cambridge University Library records, William and Frances had four other daughters: Joanna Maria (1791–1884), Julia, Anne and Patty. Joanna Maria married MP John Bonham-Carter (1788–1838) and founded the Bonham Carter family. According to the Dictionary of National Biography, 1885-1900, they also had five sons. One of them was Benjamin Smith, the Whig politician who fathered Barbara Bodichon, founder of Girton College, and the explorer Benjamin Leigh Smith.