Lieutenant-Colonel George Johnston (19 March 1764 – 5 January 1823) was briefly Lieutenant-Governor of New South Wales, Australia after leading the rebellion later known as the Rum Rebellion.
Johnston was born at Annan, Dumfriesshire, Scotland, the son of Captain George Johnston, aide-de-camp to Lord Percy, later Duke of Northumberland. Percy obtained a commission for the young Johnston as second lieutenant of marines on 6 March 1776.
He went to America with his regiment, and took part in the battle of Bunker's Hill, where he distinguished himself by seizing the colours, after the standard-bearer had been mortally wounded, and carrying them into action. During the fight his father received a wound in the breast, from which he subsequently died. Esteem for the father caused the Duke of Northumberland to become the guardian of the son, and the nobleman retained for him through life a keen personal interest.
The young officer had seen much active service against the French in the East Indies, and also on the coast of Africa, when he volunteered as an officer of the First Fleet, and came to New South Wales in 1788 with Governor Phillip holding the rank of "Captain-Lieutenant" of