Justin O'Byrne was born in Launceston on 1 June 1912, the seventh son of ten children. He was educated at St Patrick's College, Launceston.  From 1930 to 1940 he worked in the pastoral industry of south-west Queensland, working as a bullock-driver, bush blacksmith, fencer and station overseer.  He was a member and Public Relations Officer of the Miscellaneous Workers Union. 

O'Byrne joined the RAAF on 23 June 1940 and was commissioned in Canada.  He became a Pilot Officer in 1941, a Flying Officer in the same year and a Flight Lieutenant in 1943.  He was an original member of the 452 (RAAF) Fighter Squadron formed in England.  In 1941 he was shot down over St Omer, France and was held in Prisoner-of-War camps in Germany for three and a half years.  O'Byrne was discharged from the RAAF on 1 February 1946.  

He became a District Officer in the Department of Post-War Reconstruction.  He was a Delegate to the State Conference of the Australian Labor Party's Tasmanian Branch from 1946 to 1978.  At the Federal elections of 1946 O'Byrne was elected as the Senator for Tasmania, taking up his seat on 1 July 1947. 

He was a member of the Interim Council of the Australian National University (CA 504) from 29 June 1949 to 30 June 1951 and was Temporary Chairman of Committees from 27 October 1949 to 2 November 1961.  From 23 February 1950 to 2 November 1961, O'Byrne was a member of the Joint Statutory Committee on Public Works (CA 707), acting as Vice Chairman from 12 August 1954 to 4 November 1955 and from 29 January 1957 to 2 November 1961.  He was a member of the Senate Select Committee on National Service in the Defence Force during 1950 and 1951, and a member of the Joint Committee on the War Gratuity from 23 November 1951 to 5 December 1951.  In 1953 he was a member of the Parliamentary Delegation to the Coronation of Elizabeth II and a delegate to the 1953 ALP National Conference.
 
O'Byrne was a member of the Senate Standing Orders Committee (CA 725) from 16 February 1956 to 1 November 1963 and a member of the Senate Select Committee on Road Safety (CA 1706) from 1959 to 1960.  He was Opposition Whip in the Senate from 19 February 1962 to 5 December 1972 and from 15 May 1962 to 1 November 1963 he was a member of the Joint Committee on the ACT (CA 712).  During June and July 1963 he was a member of the Parliamentary Delegation to South-East Asia.  On 10 December 1965 he became a member of the Joint Select Committee on the New and Permanent Parliament House, remaining on this committee until 31 October 1966.  O'Byrne was a member of the Senate House Committee (CA 721) from 8 March 1967 to 11 November 1975 and was a member of the Senate Select Committee on Off-shore Petroleum Resources from 19 December 1967 until 1971. 

He attended the opening of the Nauru Parliament in May 1969 and was a member of successive ALP National Conferences from 1969, becoming a member of the ALP National Executive in 1972.  In September 1971 he was Parliamentary Adviser to the Australian Delegation at the United Nations General Assembly and was a member of the Senate Select Committee on Foreign Ownership and Control (CA 2489) from 2 February 1972 to 24 February 1972.
 
With the victory of the Australian Labor Party in the 1972 election.  O'Byrne became Government Whip in the Senate on 18 December 1972, holding this position until 11 April 1974. He was a member of the Joint Statutory Committee on the Broadcasting of Parliamentary Proceedings (CA 703) from 6 March 1973 to 1 June 1973 and from 9 July 1974 to 11 November 1975.  From 6 March 1973 until 11 April 1974 he was a member of the Senate Committee on Disputed Returns and Qualifications (CA 727) and from 7 March 1973 to 11 April 1974 was a member of the Senate Committee on Privileges.  In July 1974 he was elected as President of the Senate.  O'Byrne was a member of the Joint Committee on Prices from 2 May 1973 to 11 April 1974 and was Treasurer of the ALP National Executive during those two years.  He was a member of the Senate Library Committee (CA 722) from 18 July 1974 to 11 November 1974.  He became Chairman of the Senate Standing Orders Committee (CA 725) on 14 November 1974, remaining in this post until the double dissolution of 11 November 1975.  He was Joint Chairman of the Joint Committee on the New and Permanent Parliament House from 30 September 1975 until 11 November 1975.  In September 1975 he was a member of the Australian Delegation to the Papua New Guinea Independence Day celebrations.
 
After the double dissolution of 1975, Senator O'Byrne's place as President of the Senate was taken by Senator Condor Laucke (CP 224).  O'Byrne's term as Senator for Tasmania expired on 30 June 1981 and he retired from Parliament.  

O'Byrne married in 1961 and had three children.  He was a member of the Cradle Mountain-Lake St Clair National Park Board by 1955 through 1980 and the Tasmanian Scenery Preservation Board by 1965 through 1980.


Sources
 
Commonwealth Parliamentary Handbook, 1957, p 206;  1971, p 315; 
 1976, pp 127-128;  p 206;  1971, p 315;  1976, pp 127-128; 1978,
 p 140 
Who's Who in Australia, 1955, p 587; 1965, p 647; 1980, p 644

Agency associated with person unregistered

       1946-       1946: Department of Post War Reconstruction -
                         District Officer
       1950-       1951: Senate Select Committee on National Service
                         in the Defence Force - Member
23 Nov 1951-05 Dec 1951: Joint Committee on the War Gratuity - Member
   Jun 1963-   Jul 1963: Parliamentary Delegation to South-East
                         Asia - Member
10 Oct 1965-31 Oct 1966: Joint Select Committee on the New and
                         Permanent Parliament House - Member