William Swymmer (birth and death dates unknown) was a Bristol sugar merchant, involved in the slave trade. In 1667, he became a member of the Society of Merchant Venturers. He was an alderman in Bristol, and then Sheriff in 1679. Swymmer may have inherited a share in a sugar plantation in Barbados from his father. His brother and his wife were also involved in the slave trade. Records survive of the1684 correspondence from William Swymmer and William Hayman, to , the Somerset owner of a Jamaica plantation, explaining why they were unable to provide the ten slaves they had contracted to supply. The deal was illegal, as the Royal African Company had a monopoly on the British slave trade at this point.