Celtic captain Scott Brown vowed to be "relentless" in his quest for success with Aberdeen after accepting an offer to become a player-coach at Pittodrie.
The 35-year-old has agreed a pre-contract deal and will join up with newly-appointed Dons boss Stephen Glass, his former Hibernian team-mate, in the summer.
The decision will bring a hugely successful 14-year spell at Celtic Park to a close.
The midfielder has won 22 trophies, made 613 appearances - including a club-record 127 games in Europe - and scored 46 goals. He has been captain of the club for 11 years.
In a statement released by Aberdeen, Brown said: "There is no doubt I had a lot to deliberate when deciding my next steps, particularly after enjoying 14 successful years at Celtic.
"However, the opportunity to join Aberdeen, a club entering an exciting new period with my former team-mate Stephen now at the helm, was one I couldn't pass up.
"Once this season concludes, I'm looking forward to joining Stephen, the playing and coaching staff and everyone at Aberdeen FC. I am totally committed to the challenge that lies ahead in meeting the ambitions of the club and its fans.
"I still feel I have got a lot to give, not only on the pitch, but in a broader capacity as I embark on my coaching journey. I will be relentless in my quest for success for Aberdeen."
Brown has made 38 appearances this season but came under serious competition for his place from Ismaila Soro in December, and has chosen to move on with Celtic seeking a new manager.
The 55-cap former Scotland international declared that Celtic would always be in his heart.
In a statement on the Celtic website, he said: "It was a privilege to sign for this great club all those years ago and it has been an absolute honour to play for and captain Celtic for so many years."
Thanking chief executive Peter Lawwell, principal shareholder Dermot Desmond and the board for their "tremendous support", he added: "We have always enjoyed a great relationship and always worked closely together to bring our fans as much success as possible.
"I would also like to thank the great Celtic managers I have had the good fortune to work with and also so many team-mates and, of course, the Celtic fans who have given me such phenomenal support and backing over the years.
"I have always given my best to the club and always wanted the best for our fans.
"We have enjoyed some fantastic moments and success together, dominating the game in Scotland so regularly and enjoying some great European nights.
"It is a huge decision to leave this magnificent club, which has been such a massive part of my life for so long, but this is a new opportunity for me and a new chapter.
"Celtic will never leave me and the club will forever be in my heart.
"We still have work to do this season and that will of course, as ever, be my full focus as we try to bring our fans more success."
Reacting to the news of the Celtic captain's departure, interim manager John Kennedy described the Hoops captain as ‘irreplaceable’, adding that Brown’s career will serve as a template for other young players to follow.
“He’s been a terrific captain and leader of the group,” Kennedy told Celtic FC website.
“He’ll be irreplaceable in terms of what he gives us on a daily basis, his drive to be successful and how he leads the group by example every single day.
'He’s the perfect example of a modern-day professional. How he lives his life, the condition he keeps himself in and how he pushes himself every single day is incredible.
“He drives the training forward every day. He’s a massive character, a huge personality and he’s been a massive part of this club for so long and he’ll certainly be missed.”
“With young players, they might have the talent but that alone isn’t enough to be successful,” he said.
“It comes down to attitude and application. I remember Scott as a young player at Hibs and his desire on the pitch was outstanding.
“When you see him up close you realise that desire he brings on a matchday is there every day in training.
''His unselfishness to make others better, as well as himself, is an outstanding quality to have and it’s why he’s been the captain of this club for so long.
''He’s a massive part of why this club has been so successful.
“He’s one of the greats of this club, that’s without doubt, and that’ll only grow as time passes.
''He’s a huge part of the club and he always will be in my eyes.''
Aberdeen boss Stephen Glass claims Dons fans will quickly grow to love hate-figure Scott Brown.
Brown will move to Pittodrie in a player-coach role in the summer after 14 years at Celtic Park.
The midfielder has had a series of run-ins with Aberdeen players past and present such as Graeme Shinnie and Shay Logan, and wound up the Pittodrie fans who were never slow to tell him what they thought of him.
But Glass has known Brown since his formative years at Hibernian and believes he will go down well in the Granite City, on and off the park.
"There's a reason most of the fans in Scotland don't like him," Glass told Red TV.
"It's because he has been a huge part in beating everyone else's team.
"Off the pitch, you see all the charity work he does, he doesn't look for credit for a lot of the things he does. You probably don't see 90 per cent of the things Scott Brown does for people. That's the type of person he is.
"He's from a great family, his wife and kids are great people, and the Aberdeen community is going to love him."
Glass revealed he will involve Brown in all of his decision-making meetings with the staff and believes his on-field coaching role is something he had been doing for years.
"He's a natural leader and he will continue to do that," Glass added.
"It's a natural progression for him to become a coach. He is totally committed to it.
"It's not an easy decision to make for him to leave Celtic.
"I think it's the size of the possibility we have got here. He knows what I am trying to do, he knows the staff here, he knows how ambitious the chairman is and he wants to be part of it.
"It would have been very easy for him to stay at Celtic. There's a reason they want him around - he's going to be a success. And we want that to happen at Aberdeen. I was really keen to have him part of it."
Glass has kept in touch with Brown since their days at Easter Road but added there was much more to the appointment than linking up with an old friend.
"I knew him very well at Hibs," he said. "The families were quite close. You keep in touch with people you get on with and you share ideas about coaching.
"It's not about being a mate. It's bringing someone I do have a relationship with that I know is going to be a success.
"He's not leaving Celtic just because he knows me and gets on with me. He thinks this thing is going to be a success."
Glass described the signing as a "huge coup" for the club.
"His experience will be invaluable on the pitch and he is someone who will help set the standards we expect at this club," he added.
"A born competitor, with a strong appetite to win, his hands-on approach and desire to nurture will hugely benefit the development of the young, emerging talent we have here.
"Scott will be a big part of my coaching team and whilst his impact will undoubtedly be felt on the pitch where I believe he still has much to give, I am looking forward to assisting his transition into coaching."
