The New South Wales Under-18's rugby league team, also known as New South Wales Under-18's or New South Wales U18, represents New South Wales in the sport of rugby league at an under-18 age level. Between 2008 and 2019, the team played an annual fixture against the Queensland Under-18's team as a curtain raiser to a State of Origin game. The team featured players selected from New South Wales's premier under-18 rugby league competition, the S.G. Ball Cup. They were administered by the New South Wales Rugby League.
Interstate matches at an under-18 level were played between 1978 and 1985. The contests were expanded to two age groups in 1986 and three in 1987, with further changes in 1988 and 1989. From 1990 to 2007, two junior interstate matches were contested at under-17 and under-19 levels. In 2006, a New South Wales under-18 team was selected to play two matches in Auckland, New Zealand.
In 2008, with the advent of the National Youth Competition, the age levels switched to an under-16 and under-18 format to keep in line with the NSWRL's existing Harold Matthews Cup and SG Ball Cup competitions and the QRL's Cyril Connell Cup and Mal Meninga Cup competitions, which began in 2009.
New South Wales saw success in the first four under-18 Origin fixtures in this second stint, winning every game until 2012. New South Wales would win another two more fixtures in 2013 and 2014 before picking up their second loss in 2015, losing to Queensland 22-18 at the Melbourne Cricket Ground. New South Wales won each under-18 Origin fixture from 2016 to 2018. Queensland won in 2019.
Age group interstate matches were not played in 2020 due to lockdown restrictions introduced to mitigate the COVID-19 pandemic in Australia. In 2021, the age groups for Harold Matthews Cup and SG Ball Cup competitions were respectively changed from under-16 to under-17 and from under-18 to under-19. An under-19 State of Origin men's match was scheduled for 14 July 2021 but this was cancelled. Under-19 State of Origin men's matches have been held since 2022, alongside an Under 19 women's match.
Players selected for the New South Wales under-18 team are usually contracted with a National Rugby League (NRL) side but play in either the S.G. Ball Cup, Holden Cup or Intrust Super Premiership competitions. Each pre-season the New South Wales Rugby League will select an under-18 squad featuring players in contention for the mid-season fixture.
Since 2008, fifteen former New South Wales under-18 players have gone onto represent New South Wales at State of Origin level:
<small>Played as a curtain raiser to Game II of the 2008 State of Origin series.</small>
<small>Played as a curtain raiser to Game II of the 2009 State of Origin series.</small>
<small>Played as a curtain raiser to Game II of the 2010 State of Origin series.</small>
<small>Played as a curtain raiser to Game II of the 2011 State of Origin series.</small>
<small>Played as a curtain raiser to Game III of the 2012 State of Origin series.</small>
<small>Played as a curtain raiser to Game II of the 2013 State of Origin series.</small>
<small>Played as a curtain raiser to Game II of the 2014 State of Origin series.</small>
<small>Played as a curtain raiser to Game II of the 2015 State of Origin series.</small>
<small>Played as a curtain raiser to Game II of the 2016 State of Origin series.</small>
<small>Played as a curtain raiser to Game II of the 2017 State of Origin series.</small>
<small>Played as a curtain raiser to Game I of the 2018 State of Origin series.</small>