Celtic have won the Premiership title after drawing 1-1 with Dundee United at Tannadice.
The draw puts the Parkhead side on 90 points with one game to play, unable to be caught by nearest rivals Rangers.
After a goalless first half, Celtic had taken the lead against United but were pegged back by a side that booked their place in the Europa Conference League qualifiers for next season.
In the 53rd minute, Anthony Ralston burst down the right and stood up a cross to the middle, where Giorgos Giakoumakis rose to power a header past Benjamin Siegrist. Moments later United had a goal disallowed and shortly after Tony Watt hit the post with a header before Ralston cleared the rebound.
United levelled in the 73rd minute. Charlie Mulgrew strode forward and passed the ball to Dylan Levitt, who fired in a perfectly measured shot from 25 yards out to add to his collection of memorable strikes this season.
The title marks Celtic’s tenth league win in 11 years and is a second trophy for Postecoglou in his first season in charge, adding to the League Cup win earlier this season.
As Scottish champions, the team will go directly into the Champions League group stage next season.
Neil Doncaster, chief executive of the SPFL, congratulated Celtic on their achievement.
He said: “I would like to warmly congratulate Celtic’s players, management team and directors on winning the cinch Premiership.
“Celtic have now gone an impressive 31 matches without defeat in the cinch Premiership and deserve real credit for how well they have performed in recent months.
“They are worthy champions and now have the added bonus of winning direct entry to the group stages of next season’s UEFA Champions League.
“It has been a compelling season in the cinch Premiership, made all the better by the fact that supporters have been allowed back in stadiums in large numbers again, and we wish all clubs the best of luck in this weekend’s final fixtures.”