Back-to-back! Queensland hearts broken as Brumbies defend Super ...

The Super Rugby U19s grand final is run and done with defending champions ACT securing a thrilling 40-31 victory over Queensland.

It comes after NSW Waratahs clinched the U16s crown for a third straight year, downing Queensland 31-29 in a thriller.

Relive the Super Rugby U16s and U19s grand finals exclusively via Stan Sport.

Trailing 31-26 with 14 minutes remaining and struggling to contain Queensland's monster pack, the Brumbies needed something special to retain their U19s crown.

Enter backline stars Malayke Enasio and Shane Wilcox.

Already with two tries to his name, Enasio saved his best for last with a sparkling backline move linking centre partner Sam McLachlan with Samson Tuiqiri for a go-ahead score before skipper Wilcox sent best on ground Beau Morrison over in a blistering final flurry.

Morrison's 78th minute try down the right flank iced a see-sawing encounter that yielded seven lead changes as the Reds threw everything at their disposal against the defending champions.

Queensland's fearsome maul yielded two tries but was far better contained by the Brumbies, who twice denied try-magnet hooker Finlay King over the chalk and defended desperately all afternoon, particularly during the second stanza.

Wilcox paid tribute to his side's composure late in the piece with the fullback's assist for Morrison making amends for two earlier errors.

"We were just looking at each other left and right saying let's go and finish this job," Wilcox told rugby.com.au post-game.

"I was very nervous after butchering a kick late - there were 14 blokes looking at me after that one - but we stuck to it and it was a good way to finish."

"I think the whole campaign we've come together really strongly and that's a testament to our club," Morrison added.

"This has been one of the best rugby experiences of my life."

With agony comes ecstasy, of course, and the Ballymore faithful had to swallow more than their fair share.

The Reds dominated much of the second half with quickfire tries to Tom Robinson and Dom Kallquist heaping pressure on the Brumbies while Brody McLaren's boot kept the scoreboard ticking over.

Though Enasio's double will doubtless make the highlight reels - his first half effort to grubber through for himself and dot down was special - there were heroes from all sides and areas.

Queensland try-scoring number eight Vaiuta Latu was a menace all afternoon before cramp got the better of him while Reds skipper Xavier Rubens typified his side's effort, slicing through defenders and charging down a Joe Dillon clearance to set up Kallquist's try.

Meanwhile Dillon himself shone with a series of sharp kicks from hand and a pin-point cutout for Silas Pilot's 25th minute try, centre McLachlan was the perfect foil for Enasio and Lipina Ata had some magical moments in general play.

Brumbies flanker Jacob John can't be forgotten either with his third-minute try sparking the contest to life.

Brumbies 40 (Enasio 2, Pilot, John, Morrison, Tuqiri tries; McLachlan 4, Dillon cons) def Reds 31 (King, Latu, Robinson, Kallquist tries; McLaren 4 cons; McLaren pen)