John Morris has coached his last game for Cronulla after the club axed him for next season and signed Craig Fitzgibbon on a three-year deal from 2022.
Morris was told the shattering news on Tuesday afternoon and left the club immediately.
Assistant coach Josh Hannay will take over in the interim ahead of Friday's clash with Newcastle.
He served the same role at North Queensland last season after Paul Green was axed from the top job.
It comes as the Sharks confirmed a three-year deal with the Sydney Roosters assistant effective from next season.
The appointment marks Fitzgibbon's first NRL head-coaching role after knocking back offers from St George Illawarra and the Warriors and he follows his father Allan into the job.
Fitzgibbon snr coached Cronulla between 1985 and 1991.
But it comes as a cruel blow for Morris, who has taken the Sharks to the finals in both his years in charge.
"This decision was certainly not lightly taken, much discussion and consideration took place at board and management level before Craig was approached and now appointed, and we are thrilled he has accepted the position," Sharks chief executive Dino Mezzatesta said in a statement.
"Craig has served a long and successful apprenticeship under Trent Robinson at the Roosters and alongside Brad Fittler at a state level and we are confident he can emulate that success as a head coach here at the Sharks.
"However, in announcing the appointment, we need to acknowledge the contribution John Morris has made at the Cronulla club as a player, development and 20s coach, NRL assistant, and as our head coach in 2019-2020 and to this point in our 2021 season.
"As coach John has brought through a number of promising youngsters to where they are now performing at an NRL level, his work ethic can't be questioned and there is little doubt he has a bright future as a coach in the NRL."
Morris' management claim the 40-year-old was told as late as Monday he was in the pole position to coach Cronulla next year, amid constant speculation over his future.
The club's captain Wade Graham had earlier on Tuesday implored the Sharks management to hurry up and sort the mess.
However, the axing of Morris is one of the most callous in years.
He remains popular with the Cronulla playing group and has far from lost the dressing room.
The rookie coach had to deal with $353,000 stripped from the Sharks salary cap for his first two years in charge in 2019 and 2020, after breaches made during Shane Flanagan's tenure.
Despite all that, he has still taken the club to the finals in both campaigns.
"If the decision (to re-sign him) was going to be made, it should have been made already," Graham said.
"He has certainly done a commendable job over the years already.
"He walked in on not a good situation, the roster was squeezed with how it was assembled, with the salary cap fine, all the injuries he's had to deal with, all the debutants.
"He has done a great job.
"But it's got to this point now, through not the players' or John's fault, we need a decision."
Graham also declared he had no doubt Morris could take Cronulla to the next level, despite losing results against the NRL's heavyweight teams.
Meanwhile, Cameron Ciraldo could join Fitzgibbon as an assistant in a move back closer to home after impressing as Penrith's defensive coach in recent years.