Thomas (Tom) Barry (July 1, 1897-July 2, 1980) was an Irish guerrilla leader and revolutionary. Born in Rosscarbery, County Cork, Barry enlisted in the British Army during World War I and fought in Iraq (then part of the Ottoman Empire).

Upon his return to Ireland in 1919, Barry joined the Irish Republican Army (IRA) at the start of the Irish War of Independence (1919-21). He quickly rose through the ranks as an organizer and trainer of the West Cork Flying Column. This particular unit became famous for its discipline, efficiency and bravery and Barry garnered a reputation as the most brilliant field commander of the war.

On November 28, 1920, Barry's unit ambushed and wiped out an entire company of British Auxiliaries at Kilmichael , County Cork. In March 1921, his regiment — while greatly outnumbered — defeated a British force from the Essex Regiment.

In total, the British Army stationed over 12,500 troops in County Cork during the conflict, while Barry's men numbered no more than 300. Eventually, Barry's tactics made West Cork ungovernable for the British authorities who were forced to negotiate for peace.

Barry opposed the Anglo-Irish Treaty of December 6, 1921 which partitioned the country and denied Ireland full independence. He fought on the Republican side in the Irish Civil War (1922-23) and was imprisoned by the Irish Free State.

After the IRA's defeat in the Civil War, Barry was released and served as general superintendent for Cork Harbour Commissioners from 1927 to 1965. He was appointed IRA Chief-of-Staff in 1936, but resigned in 1938 after an unsuccessful campaign in Northern Ireland and his opposition to a proposed bombing campaign in England.

Barry served in the Irish Army's Southern Command during World War II, as Ireland maintained strict neutrality during that conflict.

In 1949, Barry published his memoirs of the Irish War of Independence "Guerilla Days in Ireland", which became a classic account of the war and an influential guide on guerrilla warfare.

Barry died in a Cork hospital in 1980 and was survived by his wife Leslie De Barra .