Manager Ange Postecoglou says Celtic's "overwhelming" Scottish Premiership title triumph has "taken every ounce of him" this season.
A draw at Dundee United was enough to reclaim the crown from Rangers and secure a 10th championship in 11 years.
It capped an impressive turnaround in the Australian's first season in charge, after Celtic finished 25 points behind their city rivals last term.
"It's been a hell of a season," Postecoglou told BBC Scotland.
"Our starting point was a fair way back and the way this group of players and staff has risen to the challenge - I couldn't be more proud. What it means for our supporters is unbelievable.
"It's fairly overwhelming. It's taken every ounce of me to get us where we are and when you get to the finish line, you just want to collapse. You realise just how much everyone has put into it."
Postecoglou arrived in Scotland last summer having managed mainly in his native Australia and Japan, after Eddie Howe turned down the Celtic job.
After losing three of their first six league games and falling six points behind Rangers by the winter break, Celtic are now 31 games unbeaten in the league, having also won the League Cup.
Postecoglou said the achievement is "hard for me to comprehend".
"If you had told me 12 months ago I'd be standing here - I wasn't even sure I'd be on this continent let alone be manager of this football club," the 56-year-old said.
"The dream was always to manage a famous club and try to make an impact. When something is almost a lifelong obsession and you finally get there, it's hard to put into words.
"It almost feels like two seasons in one. We've jammed in a rebuilding season and a season to win. We had a lot of work to do, and with the support of everyone at the club, we got there."
Postecoglou has done 'massive' job - analysis
Former Hearts midfielder Michael Stewart on Sportscene
It has been relentless. It makes it all the more impressive when you think about the difficult start they had to the season and the pressure that was beginning to mount on the team and Ange Postecoglou.
I'm pretty sure when he walked in he would have sensed how downbeat the place was. So to turn that around so quickly and create such a positive atmosphere, it's a massive job he's done.
Former Hibernian manager Jack Ross on Sportscene
When you look at how his team plays - it's pretty prescribed. By that I mean you know what to expect in terms of the inverted full-backs and the starting position of his wide players is so high and aggressive.
It's really difficult to play against and it was a challenge for a lot of Premiership managers to deal with. And you look at how he has recruited - he went to a different market and recruited Japanese players because he knew them and he backed them to provide him with what he needed.
It's been intriguing to see a manager from a different background come in and put his own stamp on it.
