Celtic have appointed Ange Postecoglou as their new manager on a 12-month rolling contract.
The former Australia boss was identified as the Parkhead club's top target to replace Neil Lennon after negotiations with Eddie Howe broke down, citing "reasons out of both his and Celtic's control".
Postecoglou, 55, arrives from Yokohama F. Marinos - who he led to the J League title in 2019.
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The opportunity that has been given to me is one of the greatest honours in football and the responsibility to lead our magnificent football club into the future is one that I will cherish dearly.
The Greek-born manager won two A-League titles with Brisbane Roar before he took charge of the Socceroos in 2013.
His four-year tenure saw him qualify the national side for the 2014 World Cup and win the Asia Cup in 2015.
John Kennedy had been in interim charge of Celtic since Lennon resigned in February, with the club finishing the season 25 points behind champions Rangers in the Scottish Premiership.
Celtic confirmed the news of Postecoglou's appointment in a statement to the Stock Exchange shortly before 9am which read: "Celtic is pleased to announce the appointment of Ange Postecoglou as the club's first-team manager with Ange commencing employment with immediate effect.
"The Board of Celtic is pleased to welcome Ange to the club and looks forward to working with him in the future."
On his appointment, Postecoglou said: "The opportunity that has been given to me is one of the greatest honours in football and the responsibility to lead our magnificent football club into the future is one that I will cherish dearly.
"Celtic is one of THE names in world football, of that there is no doubt - a giant of a club, a proper footballing institution and so much more - real history, real substance, real authenticity and real soul.
"I know Celtic is a true way of life for so many people and I know the demands which come with this position - I am ready to do all I can to meet those demands.
"I will be doing everything I can to get our great club back on top and, at the same time, deliver the kind of football which our fans appreciate.
"We want to entertain our fans and we want to win, these are the objectives which I always set myself and which I now begin work on.
"When you think of Celtic, you think of supporters and my dream is to see our fans back at Celtic Park with us as soon as possible.
"We all hope things are changing for the better and can see our fans soon as they are vital to everything I want to do. We need our supporters back by our side and I can't wait to be with them back in a packed Paradise.
"I have already had great discussions with (chief executive officer) Peter (Lawwell), (chief executive) Dom (McKay) and the board about their ideas and strategy for the future of the club. I know the club's new modern vision aligns very much with mine and we now look to go and deliver on this.
"In everything we do we aim to give our fans a successful team of real quality, which they are excited about and can be proud of.
"We have already begun work on our plans for adding to the squad - we aim to bring players of quality to Celtic to enhance the existing core of great talent.
"I very much look forward to meeting with the players on their return from the close season break and I can't wait to get started as Celtic manager."
What is in Postecoglou's in-tray?
Sky Sports News reporter Luke Shanley:
"Once he's gone through all the protocols and he's able to link up with the squad in pre-season, we'll have to see who comes back quickly after the Euros. But Celtic have European qualifiers straightaway - they have three rounds to get through if they are to qualify for the Champions League.
"He has to assemble a squad that's going to be much more competitive in the coming season and the issue with that is who will still be at the club at the end of the summer?
"There's a lot of talk about Odsonne Edouard leaving while Kristoffer Ajer has already gone on the record while on international duty about his future.
"So, he might have to replace some key players and that will be important for him to get the backing financially to bring in quality players to challenge domestically and in Europe to bring in new revenue. He has to build a strong relationship with the new chief executive Dominic McKay and get his philosophy across to the team.
"He looks a determined guy from the outside looking in. He will want to impose himself to ensure his message gets across."
Analysis: Second place is a disaster
Former Celtic defender Gary Caldwell told Sky Sports:
"I don't think it's the appointment that every Celtic fan or Celtic board were looking for, but sometimes these left-field appointments can actually be a positive.
"He has a good track record of winning and has good experience, but he's going to find out very quickly that he's come into a different football club, a different country where second-place isn't a failure - it's a disaster.
"He has to quickly get to grips with that mentality and what Celtic means to these supporters. Coaching is coaching and so he's clearly got that ability to work with different people but what he hasn't got is that knowledge of Celtic Football Club and what it means to supporters all around the world. They demand a certain style of football but they also demand winning.
"He's not got a season to come in and get his feet under the table by working out his methodology and style of play. He has to come in and win games from the off and hit the ground running."
Sky Sports News reporter Charles Paterson:
'With the long-awaited arrival of Neil Lennon's replacement finally confirmed, Celtic can move on from their season of discontent.
'Ange Postecoglou's appointment has come out of left-field, but became a necessity after drawn-out talks with former Bournemouth boss Eddie Howe eventually broke down.
'Howe appeared to be a shoo-in, but Celtic quickly turned their attention to the 55-year-old former Australia head coach, who will immediately be in the spotlight as he tries to rebuild a broken squad, negotiate Champions League qualifiers and establish a foothold within Scottish football, all whilst trying to settle in Glasgow.'