Stephen Hayes (26 December 1902 – 28 December 1974) was a member and leader of the Irish Republican Army from April 1939 to June 1941.
Hayes was born in Enniscorthy, County Wexford.
During the Irish War of Independence, he was commandant of the Wexford Brigade of Fianna Éireann. He took the Republican side during the Irish Civil War, during which he was interned.
Hayes was active in Gaelic Athletic Association circles in Wexford. In 1925, he helped Wexford win the Leinster Senior Football title. He also served as secretary to the county board for ten years, from the 1920s to 1930s.
Hayes joined the IRA and was on the IRA Army Council in January 1939 when it declared war on the British government.
When IRA chief of staff Seán Russell departed on IRA business to the United States (and subsequently to Nazi Germany), Hayes was left in control of the organisation. After Russell's death in August 1940 on board a German U-boat en route to Ireland, Hayes became chief of staff. His time in office was marred by controversy and it is widely believed that he served as an informer to the Garda Síochána.
Hayes had sent a plan for the invasion of Northern Ireland by German troops to Germany in April 1940. This plan later became known as Plan Kathleen. Hayes is also known to have met with German agent Hermann Görtz on 21 May 1940 in Dublin shortly after the latter’s parachuting into Ireland on 5 May 1940 as part of Operation Mainau. Hayes is known to have asked Görtz for money and arms to wage a campaign in Northern Ireland, although shortly after this meeting the original plan Kathleen was discovered. The discovery of the plan led to the acceleration of joint British and Irish military planning for a German invasion known as Plan W.