The all-conquering Shoalhaven held out a desperate Kiama to win a third straight Illawarra District Rugby Union grand final.

Their 36-5 triumph at Collegians Sporting Complex on Saturday was the Shoals 40th win on the trot, with their last loss coming more than two years ago, when beaten by Avondale on July 30, 2022.

A third title on the trot sees the Will Miller-coached outfit join a select group of IDRU teams to do so.

The latest win was built on a brilliant defensive display in the first half, with Shoals holding out a firing Kiama side before producing some brilliant counter-attacking rugby to score two unanswered tries and head to the sheds with a 12-0 advantage.

Shoalhaven captain and player-of-the-match George Miller was extremely proud of his team's resilience, especially in the opening 20 minutes.

"I think it's been a little bit of our whole year really, where the first 20 minutes of games, we just grind and our defence does us proud and then for the rest of the game our attack takes over a bit and I think that showed today again," Miller said.

The inspirational No 8 was also extremely proud to win a third title in a row with a club that was in the doldrums five to 10 years ago.

"I'm very proud. You look back five to 10 years ago and the club was in a pretty dark period. We were only able to field one side and play three games with one team," Miller said.

"It makes it that much more special to see where the club has come today, winning both grades.

"It's a very proud moment. I know a lot of the old boys would be very proud of the effort."

Shoalhaven showed early why they've won 39 games on the trot, holding out countless Kiama raid after raid in the opening 20 minutes before hitting back with two tries in the space of two minutes.

But the turning point was undoubtedly when Cows fullback Mark Asquith was sin-binned for 10 minutes for deliberately knocking the ball down.

The back-to-back champions Shoals made the most of the extra man advantage almost immediately with Alexander Wilson barging over for a try to give Shoals a 5-0 lead in the 30th minute.

They extended that lead to 12-0 a minute later after player/coach Will Miller scored, with Jack Watts adding the two.

Kiama kept coming and had a number of repeat sets close to Shoalhaven's tryline but the champions again held them out to go to the break with a 12-0 lead.

The Cows needed to be first to score after the break and they did just that, with winger Cade-Michael Patrick diving wide over to reduce the lead to seven with more than 38 minutes to play.

But Kiama were again behind the eight-ball after inspirational Shoalhaven captain George Miller busted through to score under the posts, and with Watts adding the two, the champs skipped to a 19-5 advantage.

Watts slotted another penalty goal five minutes later to further extend Shoals lead to 22-5.

Kiama's fightback efforts weren't helped when Matt Hobbs was binned for 10 minutes and then the creative Nico Cowley was forced off the field with concussion-like symptoms.

The champions again made the most of their one-man advantage with halfback Dominic Bullock crossing for a smart try, which Watts converted to extend Shoals lead to 29-5.

The machine that is Shoalhaven continued to attack their vanquished opponents, with winger Angus Templeton crossing for the champions fifth try of the game.

Shoalhaven player/coach Will Miller said his team had achieved something very special.

"You can see what this means to all our fans and old boys. There are a lot of people here and they're very proud of what we've achieved, and so are we," he said.

"It's been a long, long time since anyone's gone three in a row. Winning a competition is special on its own, winning three in a row is something very special.

The fact that second grade also won on the same day is outstanding and it's why everyone is very proud."