John Joseph Cahill, also known as Joe Cahill or J. J. Cahill, was a long-serving New South Wales politician, railway worker, trade unionist and Labor Party Premier of New South Wales from 1952 to his death in 1959. Born the son of Irish migrants in Redfern, New South Wales, Cahill worked for the New South Wales Government Railways from the age of 16 before joining the Australian Labor Party. Being a prominent unionist organiser, including being dismissed for his role in the 1917 general strike, Cahill was eventually elected to the Parliament of New South Wales for St George in 1925.

The premier of New South Wales is the head of government in the state of New South Wales, Australia. The Government of New South Wales follows the Westminster Parliamentary System, with a Parliament of New South Wales acting as the legislature. The premier is appointed by the Governor of New South Wales, and by modern convention holds office by their ability to command the support of a majority of members of the lower house of Parliament, the Legislative Assembly.