David Barclay of Youngsbury (1729–1809), also known as David Barclay of Walthamstow or David Barclay of Walthamstow and Youngsbury, was an English Quaker merchant, banker, and philanthropist. He is notable for an experiment in "gratuitous manumission", in which he freed an estate of Jamaican slaves, and arranged for better futures for them in Pennsylvania. His legacy was as one of the founders of the present-day Barclays Bank, a century ahead of its formation under that name, and in the brewing industry.