The Jersey Flegg Cup was a junior rugby league competition played in New South Wales, contested among teams made up of players aged under 20. The competition was administered by the New South Wales Rugby League (NSWRL) and run concurrently with the National Rugby League (NRL). It ceased at the end of the 2007 season to make way for the NRL's new Under 20s tournament, the National Youth Competition (referred to as the Toyota Cup), which commenced in 2008.

The Cup began as an Under 19s age group competition, changing to Under 20s with the advent of the NRL in 1998. It was originally held as part of the NSWRL's Junior Representative Competition, which was played over 9–12 weeks early in the season. It then evolved to become a full season competition played over 26 rounds, culminating with the Grand Final held on the same day as the First Grade Premiership decider.

The competition was named for Harry "Jersey" Flegg, a former player (playing in 1908 and 1909 for Eastern Suburbs) and prominent administrator of the game between 1909 and 1960.

2017 was the end of the Nation Youth Competion, and it reverted back to the Jersey Flegg Competion
2020 New Zealand Warriors pulled out of the competition, 2021 Newcastle Knights pulled out of Competition
2021 aged group changed from 20 to 21
2022 Newcastle Knights rejoined the competition

Placed

1988 finishing
1989 finishing
1990 finishing
1991 finishing 1st (Grandfinal Winner)
1992 finishing (Grandfinal Winner)
1993 finishing 5th
1994 finishing
1995 finishing 5th
1996 finishing
1997 finishing
1998 finishing
1999 finishing
2000 finishing 10th
2001 finishing
2002 finishing 5th
2003 finishing 7th
2004 finishing 10th
2005 finishing 4th
2006 finishing 1st
2007 finishing 6th
2018 finished 1st
2019 finished 7th,
2020 competeition cancelled
2021 Cancelled due to Covid
2022 finished 2nd
2023 finished 11th

Teams completing in Competition

Grandfinal Winners
NSW Jersey Flegg