Sir Alexander Johnston, PC, FRS (25 April 1775 – 6 March 1849), was born in Carnsalloch, Dumfriesshire but moved with his family to India when his father received a posting in the Madras Presidency. He returned to England to study law. Johnston became a British colonial official who served as third Chief Justice of Ceylon and second Advocate Fiscal of Ceylon. He introduced a range of administrative reforms to the country and was an advocate of the rights of the native people. He was also an orientalist and along with Henry Thomas Colebrooke and others he was a founding member of the Royal Asiatic Society of Great Britain and Ireland.