William Forster (23 March 1784 – 27 January 1854) was a preacher, Quaker elder and a fervent abolitionist. He was an early member of the British and Foreign Anti-Slavery Society in 1839. It was William and Stephen Grellet who introduced Elizabeth Fry to her life's work with prisons, but it was William's brother, Josiah, who accompanied Fry on her tour and inspection of prisons in France.