Marmaduke Gwynne (1691–1769) was a Welsh squire, and an early and influential Methodist convert. He was a scion of the Gwynne family of Glanbrân near Llandovery. Gwynne married well and employed Theophilus Evans as an Anglican private chaplain. He was converted to Methodism by Howell Harris. He served as a legal adviser and financial supporter to the Methodists and his daughter Sarah married Charles Wesley.