George Onslow (28 April 1731 – 12 November 1792) was a British politician and army officer, the eldest son of Richard Onslow and his second wife Pooley, and the nephew of Arthur Onslow, Speaker of the House of Commons.
Onslow was born in Guildford, Surrey in 1731. He entered the British Army as an ensign in the 1st Regiment of Foot Guards on 17 February 1748 and became a captain in John Guise's Regiment of Foot on 12 January 1751.
Onslow married Jane Thorp, sister of Robert Thorp, on 29 July 1752. They had five children:
Onslow continued to rise in the Army, and was promoted major in the 57th Regiment of Foot on 3 August 1757. He returned to his original regiment, the Foot Guards, on 27 March 1759 with the rank of captain-lieutenant and was promoted lieutenant-colonel on 7 November 1759. He entered the House of Commons in March 1760 upon the death of his father, replacing him as one of the members for Guildford. He was known as "Colonel Onslow" in the Commons to distinguish him from his first cousin George Onslow, later Earl of Onslow.
Onslow began his parliamentary career as one of the Rockingham Whigs, like his cousin George. Onslow was the only member to declare that issue no. 45 of The North Briton was not a libel on the King, and he opposed the expulsion of Wilkes from the House. As a reward for his support of the Rockingham administration, he received the post of Out-Ranger of Windsor Forest for life in 1765. In 1766, he voted for the repeal of the Stamp Act.