Sir Ralph Abercromby KB (sometimes spelt Abercrombie) (7 October 1734 – 28 March 1801) was a Scottish soldier and politician. He rose to the rank of lieutenant-general in the British Army, was noted for his services during the Napoleonic Wars, and served as Commander-in-Chief, Ireland.

He twice served as MP for Clackmannanshire and Kinross-shire, and was appointed Governor of Trinidad.

He was the eldest son of George Abercromby of Tullibody, Clackmannanshire, and a brother of the advocate Alexander Abercromby, Lord Abercromby. He was born at Menstrie, Clackmannanshire. Educated at Rugby and the University of Edinburgh, in 1754 he was sent to Leipzig to study civil law, with a view to his proceeding to a career as an advocate.

On returning from the continent he expressed a strong preference for the military profession, and a cornet's commission was accordingly obtained for him (March 1756) in the 3rd Dragoon Guards. He served with his regiment in the Seven Years' War, and the opportunity thus afforded him of studying the methods of Frederick the Great moulded his military character and formed his tactical ideas.