Denis Cullen (19 August 1886 – 26 November 1971) was an Irish Labour Party politician and trade union official. A baker by trade, during the 1910s he emerged as a leading figure in the Dublin branch of the Irish Bakers' National Amalgamated Union. At the 1918 national convention – at which the union's name was changed to the Irish Bakers, Confectioners, and Allied Workers Amalgamated Union – Cullen was elected national general secretary, commencing a twenty-five-year tenure (1918–1943), during which he was chief negotiator for both the national union and Dublin branch. He was also prominent in the leadership of the Irish Trades Union Congress (ITUC), serving almost continually on the national executive (1920–1939, 1940–1943), as treasurer (1929–1930), and for two terms as president (1925–1