John Thomas Lang, usually referred to as J. T. Lang during his career and familiarly known as "Jack" and nicknamed "The Big Fella", was an Australian politician, mainly for the New South Wales Branch of the Labor Party. He twice served as the 23rd Premier of New South Wales from 1925 to 1927 and again from 1930 to 1932. He was dismissed by the Governor of New South Wales, Sir Philip Game, at the climax of the 1932 constitutional crisis and resoundingly lost the resulting election and subsequent elections as Leader of the Opposition. He later formed Lang Labor that contested federal and state elections and was briefly a member of the Australian House of Representatives.

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.