Lieutenant John Clarkson (1764–1828) was a Royal Navy officer and abolitionist, the younger brother of Thomas Clarkson, one of the central figures in the abolition of slavery in England and the British Empire at the close of the 18th century. As agent for the Sierra Leone Company, Lieutenant Clarkson was instrumental in the founding of Freetown, today Sierra Leone’s capital city, as a haven for chiefly formerly enslaved African-Americans first relocated to Nova Scotia by the British military authorities following the American Revolutionary War.