Matthew Caffyn (christened 26 October 1628 – buried June 1714) was a British General Baptist preacher and writer.
He was born at Horsham, Sussex, the seventh son of Thomas Caffin, by Elizabeth his wife (in Mark Antony Lower's 'Worthies of Sussex' it is incorrectly said that his father was German). According to family tradition, Elizabeth was a direct descendant of a martyr of the Marian Persecutions, possibly John Forman, who was burnt at East Grinstead in 1556. Matthew's father Thomas Caffin was employed by the Onslow family, who owned Drungewick Manor close to the border of Sussex and Surrey. When Matthew was around 7 years old, Richard Onslow adopted him as a companion for his own son Richard. The two boys were educated at a grammar school in Kent and in 1643 both were sent to All Soul's College, Oxford to study for the Church of England ministry. However he soon faced difficulties at All Soul's College for questioning infant baptism and the Trinity and then advocating Baptist tenets. The university attempted to induce Caffyn to suppress his own views, but failed and he was then expelled in 1645. Now 17, Caffyn returned to Horsham and was installed at Pond Farm in Southwater by is adoptive father. He quickly joined a General Baptist church there, and was appointed assistant to the local General Baptist minister, Samuel Lover. Caffyn's apparent campaigning vigour brought about a significant increase in local adherents, and by 1648 he had taken over the ministry from Lover.
Caffyn preached assiduously in Sussex villages, and was five times imprisoned for unauthorised preaching. In 1655 two quakers from the north, Thomas Lawson and John Slee, were on a mission in Sussex. Lawson had been a beneficed clergyman in Lancashire, known as a botanist. But in his encounter with Caffyn he descended to abuse. Caffyn had expressed his views in a quakers' meeting at Crawley, and the discussion had been continued on 5 Sep at Caffyn's house near Southwater, just south of Horsham. A pamphlet war resulted. One Baptist participan, Joseph Wright, was removed by an incarceration in Maidstone gaol; and when he came out, Caffyn's heresies seemed to him to require attention rather than those of the quakers. This later led to serious trouble for Caffyn.