John Hamilton Mortimer ARA (1740–1779) was a British figure and landscape painter and printmaker, known for romantic paintings set in Italy, works depicting conversations, and works drawn in the 1770s portraying war scenes, similar to those of Salvator Rosa.
Mortimer became President of the Society of Artists in 1774, five years before his death, at age 39.
Mortimer was born on 17? September 1740 at Eastbourne. His father was a customs officer, a dealer in flour and owner of several mills. By 1757, while he was still young, Mortimer was studying in London at the Duke of Richmond's Academy. During this time he became a friend of Joseph Wright, a fellow student at the Academy - a friendship which would endure throughout Mortimer's life. Mortimer is also known to have had some professional relationship with the artist Samuel Ireland, who was involved with etching his work. At the St Martin's Lane Academy his fellow students included Thomas Jones and William Pars. In 1759 Mortimer won a first prize for a study after Michelangelo's Bacchus and a second prize for a life drawing.
He began to exhibit his works on a regular basis in the early 1760s, becoming an active member of the Society of Artists, which awarded him prizes for paintings of subjects from British history in 1763 and 1764. The second of these prizes was for a picture entitled St Paul Preaching to the Ancient Druids in Britain (now in the Guildhall in High Wycombe). He became president of the society in 1774.