The title, which United won from third place, marks Aloisi's first silverware as a coach and stopped City from becoming the first team to complete back-to-back premiership-championship doubles.

After finishing 10th last season, United took a gamble on Aloisi, who hadn't coached since 2018 after a rough end to his time at Brisbane Roar and a brutal first job at Melbourne Heart.

It paid off in spades as they became the second team, after Melbourne Victory in 2017-18 to win from outside the top two, despite being without Alessandro Diamanti, Rene Khrin and Nikolai Topor-Stanley.

Aloisi, best known for his famous 2005 penalty against Uruguay that sent the Socceroos to their breakthrough 2006 World Cup, believed his coaching triumph stacked up.

"It does. It really does," he said.

"Where the club has come from and, you know, we've talked about last year, a lot of people were talking about last year, how it wasn't a great year for the club.

"It's only three seasons old and to be able to do what we did tonight and from the beginning of the season ... it's amazing.

"It was an amazing feeling, amazing night. I am so happy for the football club as a whole.

"Not even tonight they were tipping us: $5 (the bookmakers) were giving us. If I could bet, which I'm not a betting man, but if I could bet I would've put so much money on that.

"They must've lost a shitload of money on that."

Serbian striker Aleksandar Prijovic won the Joe Marston Medal as United's focal point, while central defenders Leo Lacroix and Tomoki Imai blanketed Jamie Maclaren.

United scored in the second minute when former City man Ben Garuccio whipped in a corner to the near post and the ball bounced off Nuno Reis' head for an own goal.

They doubled their lead on the half-hour when a blocked shot ricocheted off Connor Pain's face, took a touch off City's Connor Metcalfe and skidded into the path of Prijovic, who coolly finished.

The goal was originally chalked off but, after a quick review with VAR Kris Griffiths-Jones, referee Chris Beath awarded it.

There was controversy in the 44th minute when City's Carl Jenkinson appeared to headbutt Pain but wasn't punished.

City peppered United's goal after the break.

Curtis Good powered a header against the bar in the 48th minute and Metcalfe headed over in the 54th.

Jamie Young pulled off two brilliant saves, denying Andrew Nabbout's fierce strike in the 66th and Galloway's 81st-minute long-range effort to keep his clean sheet.

"When you go behind early in a final, it's very difficult to get back, especially in a grand final," City coach Patrick Kisnorbo said.

"Sometimes you need to hurt to grow a bit. I'm sure (the players are) feeling the hurt now but they've had a fantastic couple of years, so I couldn't be much prouder."

Australian Associated Press