The nib Newcastle Knights Harold Matthews side came from two tries down to win a thrilling grand final 26-20 against the Manly Sea Eagles at Leichhardt Oval on Saturday afternoon.

It was a courageous display from the Under 16s side, after going through a nervy start to the showdown.

Just seconds before the final siren the young Knights were still trailing by six points, but a Patrick Achurch try right on the buzzer sent the game to extra time.

It was captain Jaron Purcell that won the game in extra time, barging over from close range to give the Knights their fourth Harold Matthews title.

"To be undefeated premiers in 2017 is an amazing feeling," Purcell said after the match.

"We have players from Newcastle, Maitland, the Hunter Valley and the Central Coast, to pull a team of 16-year-old boys from country areas to win a NSW State competition is amazing.

"A special thank you to our parents and staff for the time, effort and support they put in to help us achieve our goals this season."

Max Buderus got the scoring underway for the Knights right before half time, jabbing through a grubber for back rower Riley Meyn to score.

Up until that point the Knights had been well and truly dominated by an impressive Manly side, and even though the Sea Eagles scored again early in the second half, the red and blues started building confidence.

Imposing prop Christian Ma'anaima was second try scorer for the Knights in the 36th minute, and Buderus converted to make the score 14-10 to Manly.

Soon after Meyn got his second try following an excellent run, and it looked as though the Knights had the upper hand.

But Albert Hopoate scored for Manly against the run of play with just nine minutes left on the clock, and it was clear that the Knights would have to dig deep.

Achurch came up with the most important try of the day right on full time, and the rest was history as the Knights claimed the win in extra time to complete an unbeaten 2017.

SUMMARY

Knights 26 (T: Meyn 2, Ma'anaima, Achurch, Purcell, G: Buderus 3/5)

Sea Eagles 20

TEAM

1. Bradman Best, 2. Maile J Townsend, 3. Darcy Heaney, 4. Cooper Jenkins, 5. Patrick Achurch, 6. Max Buderus, 7. Kobe Davies, 16. Ben Olsen, 9. Mitch Black, 10. Christian Ma’anaima, 11. Riley Meyn, 12. Harry Croker, 13. Jaron Purcell. Interchange: 8. Thomas Affleck, 14. Ryan Potts, 15. Tyler Doney, 17. Sione Tuitupou Kutu.