Sir Gyles Isham, 12th Baronet (31 October 1903 – 29 January 1976) was an English aristocrat, actor, and historian.

Enlisting in the British Army during the Second World War, in 1940 he was commissioned as an officer into the King's Royal Rifle Corps and served in Libya in the Western Desert Campaign, by 1943 reaching the rank of lieutenant-colonel.

He also succeeded in 1941, during his Libyan service, to the Baronetcy of Lamport with the death of his father, thereby becoming Sir Gyles Isham.

He was a trustee in 1964 of the National Portrait Gallery, and president between 1968 and 1976 of the Association of Genealogists, during which time he wrote several books and pamphlets on the history of Northamptonshire.

Sir Gyles died on 29 January 1976 at the age of 72 at St. Matthew's Nursing Home, Northampton, England.