State of Origin is the annual best-of-three series of rugby league football matches between the Blues and the Maroons, who represent the Australian states of New South Wales and Queensland, respectively. Touted as Australian sport's greatest rivalry, the State of Origin series is one of the country's and the region's premier sporting events, attracting a huge television audience and usually selling out the stadiums in which the games are played. Despite the existence of international tournaments and State of Origin being a domestic competition, it is frequently cited as being the highest-level of rugby league played anywhere in the world.

Players are selected to represent the Australian state in which they played their first senior rugby league, hence the name 'state of origin'. Prior to 1980 players were only selected for interstate matches on the basis of where they were playing their club football at the time. In both 1980 and 1981 there were two interstate matches under the old selection rules and one experimental "State of Origin" match. From 1982 onwards a best-of-three match series has been played around the middle of the rugby league season for the State of Origin shield. Since the inception of the series, total victories for each side were formerly extraordinarily even; however, since 2006, Queensland has dominated the competition, winning all seven of the following series.