Rugby league has the highest spectator numbers of the various codes of football in New South Wales. It began in Australia in 1907, when the New South Wales Rugby League was formed as a professional competition, following the rules of the Northern Rugby Football Union in England. Since then the state has been one of the major centres of the code.

The headquarters of the Australian Rugby League and National Rugby League (NRL) are in Sydney, which is home to 8 of the 16 National Rugby League (NRL) clubs (Sydney Roosters, South Sydney Rabbitohs, Parramatta Eels, Cronulla Sharks, Wests Tigers, Penrith Panthers, Bulldogs and Manly-Warringah Sea Eagles), as well as being the northern home of the St George Illawarra Dragons, which is half-based in Wollongong. A tenth team, the Newcastle Knights are located in Newcastle.

The premier state-level league is the New South Wales Cup, involving reserve teams from NSW and Canberra based NRL clubs as well as the first teams from other clubs. Country football is overseen by the New South Wales Country Rugby League. Annual matches between Country Origin and City Origin teams are held.

The annual State of Origin series between the New South Wales Blues and the Queensland Maroons is the most popular sporting event in NSW. Sydney has hosted many State of Origin matches since the series began in 1980. The 3 game series are held in Sydney and Brisbane with the first and third games in one city and the second in the other. These rotate every year, so if two games are played in Sydney one year, then those games are played in Brisbane the next.