Scoring his first goal for Auckland in his 58th match, midfielder Howieson's 60th-minute volley from well outside the area took a deflection before fizzing past wrong-footed goalkeeper Harrison Devenish-Meares.

That was all the hosts needed to secure the trophy in their second season, sending most of a sold-out crowd of 28,374 at Auckland's Mount Smart Stadium into ecstasy.

"I'm so stoked. This was our goal from the start of the season. And we're here and we've done it," Auckland forward Jesse Randall said.

"I'm so proud of all the boys and the staff, we've put so much work into this."

Auckland joined a select group of cross-border winners in world soccer, emulating AS Monaco, which has won eight titles in France's Ligue 1 and Northern Ireland's Derry City, twice a league winner in the Republic of Ireland.

Auckland was little more than a concept a few years ago but, with the backing of American billionaire Bill Foley, the Black Knights' entry into the Australian top flight has been a stunning success, leaving New Zealand's established team in the competition, Wellington Phoenix, in its dust.

In their A-League debut, Auckland won the Premier's Plate for finishing top of the table at the end of the regular season but the ultimate fairytale finish eluded it in the play-offs.

It suffered a semi-final choke at its home ground, losing 2-0 against Melbourne Victory after taking a 1-0 lead from the first leg back in Australia.

All that was swept aside on Saturday when it held firm in a tense finish against the A-League's most successful team.

For Auckland boss Steve Corica, it was a night of mixed emotions as he celebrated his third A-League title as coach against his former team.

Corica delivered Sydney back-to-back titles in 2019-2020 and, as a player, he scored the winner for the Sky Blues in the inaugural 2006 grand final against Central Coast Mariners.

However, he left Sydney on a sour note, sacked three games into the 2023-2024 season.

Bidding for a record-extending sixth championship, Patrick Kisnorbo's Sydney had scraped into the grand final via a penalty shootout after a last-gasp equaliser in the semi-final against Newcastle Jets.

But there was no late rally at Mount Smart.

Sydney captain Rhyan Grant's quest for a record-equalling fifth A-League title as a player fell short after having a late chance to equalise.

He latched on to a pinpoint cross from English winger Joe Lolley on 83 minutes but sent his glancing header just over the bar.

By that stage, Sydney was lucky to be only a goal down, with Randall having missed a glorious chance to bury the Sky Blues just moments earlier when he blazed over from short range and with the goal at his mercy.