The 2003 NRL premiership was the 96th season of professional rugby league football in Australia and the sixth run by the National Rugby League. Fifteen teams competed, with the Manly-Warringah Sea Eagles returning in place of their failed joint-venture club, the Northern Eagles. Ultimately, the Penrith Panthers defeated reigning champions, the Sydney Roosters in the 2003 NRL grand final, claiming their first premiership since 1991.

Season 2003 brought in the new "golden point" extra time rule, where after 80 minutes, if the game was drawn, then 10 minutes of extra time was played until one team scored the winning point(s). The salary cap for the 2003 season was A$3.25 million per club for their 25 highest-paid players.

The first round of the Premiership improved on the previous year's in terms of attendance and television ratings. The major story this season was the resurgence of the Penrith Panthers, who defied the critics and naysayers to win their second premiership in their illustrious history since joining the competition in 1967. Coached by John Lang and captained by Craig Gower, the Panthers were the surprise minor premiers, dominating the competition despite consistent disparagement from many sources, and would continue their outstanding form in the finals, beating the Broncos, Warriors and finally the Roosters in the grand final.

The Dally M Medal ceremony was cancelled by the NRL after negotiations with the players' union, the Rugby League Professionals Association, stalled. All votes for the award were destroyed. It was later revealed that with one round of the regular season to play, Craig Gower was leading both Brad Fittler and Clinton Schifcofske by one point in the overall points tally. However, with the ceremony officially cancelled more than a week out from the awards, no points were allocated in the final round of the season.

At the end of the season, Chris Anderson would lose his job at Cronulla-Sutherland, while Peter Sharp was dismissed as the Sea Eagles coach. Trainer and former Manly star, Des Hasler would replace Sharp as head coach in 2004.

Also at the end of the season, a squad of players from the NRL premiership went on the 2003 Kangaroo tour.

A major flaw of the fixture was that the previous season's Grand Finalists, the New Zealand Warriors and Sydney Roosters, did not meet until the penultimate round of the regular season.

The lineup of fifteen teams for the 2003 premiership remained unchanged from the previous season, except that the Manly-Warringah Sea Eagles name and colours rejoined the competition since their merger with North Sydney Bears in 1999, taking the place of the failed Northern Eagles, Manly Warringah returned as a stand-alone in 2002, but played under the Northern Eagles name and colours