Lieutenant-General Sir Sydney John Cotton GCB (2 December 1792 – 19 February 1874) was a British Army officer.

Born the second son of Henry Calveley Cotton of Woodcote, Oxfordshire, England, and his wife Matilda, daughter and heiress of John Lockwood of Dews Hall, Essex, Cotton joined the British Army in 1810 as a Cornet in the 22nd Light Dragoons.

He served extensively in Australia (1835 to 1842) including being the commandant of the Moreton Bay penal colony (now the city of Brisbane) from 1837 to 1839.

For his frontier services, Cotton was appointed KCB and after returning to England he became General Officer Commanding Northern District in July 1865.

[2] He was promoted to lieutenant-General in 1866 and, after publishing "Nine Years on the North-West Frontier of India from 1854 to 1863" in 1868, he was advanced to GCB in 1872.