Socceroo Rhyan Grant was the hero Sunday as Sydney FC beat Melbourne City 1-0 in extra-time to win the A-League Grand Final and etch their name in the history books.

The tireless defender timed his run perfectly to meet a cross from Luke Brattan and chest the ball home after the sides went scoreless over 90 minutes.

In front of 7,500 fans at Sydney's Bankwest Stadium -- the most allowed under coronavirus restrictions -- it was enough to earn Steve Corica's team back-to-back titles.

It also handed them their fifth overall -- a feat no other team has achieved in the league's 15-year history.

"It's nice, I maybe got a little bit lucky (with the goal) but happy days," said Grant after crushing City's dreams of a maiden crown.

"It was a Grand Final and a bit end-to-end at times, and a bit cagey. We just had to ride that out and make sure when we got chances we took them.

Despite the disappointment of defeat, it was City's best-ever season.

With French tactician Erick Mombaerts at the helm they amassed their biggest points tally, enjoyed their highest finish on the ladder, made the final and qualified for the AFC Champions League.

Sydney had the clear advantage on paper -- it was their sixth final to City's first and they came into the game having won the coronavirus-affected regular season premiership.

Under A-League rules, the teams that finished the season first (Sydney) and second (Melbourne City) progressed straight to the semi-finals.

Sydney beat Perth Glory 2-0 while City eased past Western United by the same scoreline.

"It is not easy going back-to-back, only one team has ever done it before in the history of the league, so it really means a lot to the team," said manager Steve Corica.

"We set out sights at the start of the year to win the premiership and do the double, so full credit to the boys. They were sensational all year."

City were sharper early in the game and they thought they'd opened their account when Harrison Delbridge drilled the ball into the net.

But the VAR showed teammate Lachlan Wales was offside and obstructed the goalkeeper.

It was a fortunate escape for Sydney, with Melbourne enjoying their own slice of luck when an Adam le Fondre penalty appeal was ignored by the referee. Replays showed it was a questionable decision.

Englishman Le Fondre and former Serbia international Milos Ninkovic both had opportunities early in the second stanza, but City goalkeeper Tom Glover did well to keep them out.

Scott Galloway produced City's best chance, forcing a diving save from Andrew Redmayne, but despite pressure from both sides it went to extra time.

Sydney proved hungrier and Grant finally got the breakthrough on 100 minutes with Glover pulling off some fine saves as they pressed hard for a second.