Colonel Alexander John Montgomery (1720 – 29 September 1800) was an Irish politician. He was born in 1720, the eldest son of Thomas Montgomery, M.P. for Lifford, and his wife Mary Franklin. His youngest brother was the American Revolution war-hero, Major-General Richard Montgomery. He was elected Member of Parliament as an Independent for County Donegal in the General Election of 1768 and represented that constituency until August 1800. He was also High Sheriff of Donegal in 1773.