Lemuel Francis Abbot (c. 1760–5 December 1802) was an English portrait painter, famous for his portrait of Horatio Nelson, 1st Viscount Nelson (currently hanging in the Terracotta Room of number 10 Downing Street) and for those of other naval officers and literary figures of the 18th century.

Born in Leicestershire, the son of a clergyman, in 1760 or 1761, he became in 1775 a pupil of Francis Hayman and lived in London.

Although he exhibited at the Royal Academy, Abbott never became an Academician. He became insane when he was about 40 and was attended by Dr Thomas Munro (1759–1833), the chief physician to Bethlem Hospital and a specialist in mental disorders. Munro also treated the insanity of King George III (1738–1820). Abbott died in London on 5 December 1802.