O'Sullivan, Martin (1891–1956), trade unionist and politician, was born in 1891 in Ennistymon, Co. Clare. Educated locally at the CBS, he joined the Midland & Great Western Railway Co. as a clerk and worked in Sligo and Cavan before his appointment as station master at Recess, Co. Galway. After the amalgamation of the Midland & Great Western and Great Southern railways, he was transferred to Dublin as chief pay clerk at Inchicore. Prominent in the trade union movement, he was secretary and chairman of the Irish Council of Railway Clerks Association, chairman of the Dublin Trades Council, and a member of the national executive of the Irish Trade Union Congress.
First elected to Dublin corporation in October 1930 as a Labour candidate, he was reelected at every municipal election until he stood down in 1950. Elected to the corporation as an alderman in 1942, in June 1943 he was unanimously elected lord mayor of Dublin, the first member of the Labour party to hold the office. His reelection as lord mayor in June 1944 caused a split among Labour members of the corporation when James Larkin (qv) objected on the grounds that the same person should not hold the office for two consecutive years. He served on most corporation committees and represented the corporation on the Dublin port and docks board, of which he was chairman in 1946–8, and the commissioners of Irish lights. Having lost the Labour nomination for Sligo–Leitrim in the June 1927 general election to Archie Heron (qv), he was defeated in the Dublin North constituency in the 1932 general election but was elected for the same constituency in the following year. He served as a TD until 1951, representing Dublin North (1933–8), Dublin county (1938–43), Dublin North-West (1943–8) and Dublin North Central (1948–51). Considered by former Labour party leader Thomas Johnson (qv), a close friend, to be a potential party leader (a view that was not widely shared within the party), in November 1949 he became leader of the Labour parliamentary party, but left the post on health grounds in November 1950. As a local and national politician he was most concerned with issues of housing and unemployment, and in a lecture delivered at the Gaiety Theatre on 21 November 1937 he called for unemployment to ‘be made a national question and raised above the exigencies of party politics’ (Catholic Bulletin, Dec. 1937, 910). Retiring from politics in the early 1950s due to ill health, in 1953 he was appointed to the board of the Great Northern Railway and in 1954 appointed a member of the board of Aer Rianta by the minister for finance. A keen golfer and a member of Clontarf golf club, he supported plans to build municipal golf links in Dublin. In Dublin he lived at 3 St Michael's Gardens; 7 St Mobhi Road, Glasnevin; 74 Ballymun Road, Glasnevin; and ‘Kilmanaheen’, Sutton, with his wife Mary and their son and two daughters. He died 20 January 1956 in Dublin, leaving an estate of £6,914.