Chelsea have announced Graham Potter as their head coach on a five-year contract.
Potter becomes the first managerial appointment of the Todd Boehly era following his summer takeover. The American is still acting as sporting director having moved on director Marina Granovskaia, chairman Bruce Buck and technical and performance advisor Petr Cech in a complete overhaul of Roman Abramovich's trusted staff.
Sky Sports News understands Chelsea have paid Brighton a total of £21.5m in compensation for Potter and the other 4 members of staff that have followed him to Stamford Bridge.
'We are thrilled to bring Graham to Chelsea," said Boehly after Potter's appointment. "He is a proven coach and an innovator in the Premier League who fits our vision for the club. Not only is he extremely talented on the pitch, he has skills and capabilities that extend beyond the pitch which will make Chelsea a more successful club.
"He has had a major impact at his previous clubs and we look forward to his positive impact at Chelsea. We look forward to supporting him, his coaching team and the squad in realising their full potential in the coming months and years."
The 47-year-old will be followed from Brighton to Chelsea by Kyle MacAulay, the recruitment expert that's been with him since his Ostersunds days, assistant head coach Billy Reid, goalkeeper coach Ben Roberts and first-team coach Bjorn Hamburg.
"I am incredibly proud and excited to represent Chelsea FC, this fantastic football club," said Potter. "I am very excited to partner with Chelsea's new ownership group and look forward to meeting and working with the exciting group of players and to develop a team and culture that our amazing fans can be proud of.
"I would also like to place my sincere thanks to Brighton & Hove Albion for allowing me this opportunity and in particular Tony Bloom and all the players, staff and supporters for their continued support during my time at the club."
Potter's first game in charge will be a west London derby at Fulham on Saturday, kick-off 12.30pm.
Tuchel was sacked on Wednesday in the wake of Chelsea's 1-0 loss to Dinamo Zagreb in the Champions League and just six games into the new Premier League season.
Chelsea owner Boehly met Potter in central London on Wednesday afternoon for what was described as "positive talks" about the Brighton manager's future role at Stamford Bridge and the club's plans to develop the whole football operation.
Meanwhile, Brighton U21 coach Andrew Crofts will take charge of the Seagulls on an interim basis, supported by assistant Shannon Ruth, set-play coach Nick Stanley, Adam Lallana and assistant goalkeeping coach Jack Stern.
Sky Sports pundit Jamie Carragher:
"It's a very ruthless club and I'm not sure [Graham Potter] is the right fit - maybe Chelsea are saying they want to do things differently in the future in terms of having a coach in charge rather than a manager or they do things behind the scenes differently. But if I was Graham Potter, I would find that very hard to believe that they're going to do things differently. They've just got rid of a manager six games into the season.
"It's a huge step up in his managerial career and Chelsea are still one of the top clubs. They are still world champions right now, but you fear for Graham Potter that he'll be in the same boat as every other Chelsea manager has for the last 10 years - unless he gets results instantly they'll be getting themselves another new manager in 12 months."
Sky Sports' Ron Walker:
If Chelsea are serious about rebuilding the club from top to bottom, a long-term job whoever is in charge, they have picked a man who ticks all the right boxes in Brighton's Graham Potter.
Six games into the new season, his now former-Seagulls side sit three points and two places above Chelsea in the table, despite significantly inferior resources to the Blues and any of the other teams around them.
It's not about that small sample though. What Potter has been building at Brighton has been far longer in the making. The obvious product of his philosophy has been their brand of passing football, but his work on the south coast has run far beyond the tactics board.
That decision to pull the trigger only 100 days into his ownership will raise eyebrows about appointing a man like Potter, who finished 15th and 16th in his first two seasons at the Amex Stadium.
But if Boehly's rationale was, as he has privately stated, to appoint a coach whose long-term vision he can better align with then Thomas Tuchel's dismissal, though still harsh, may prove a shrewder move than it appeared at the time.
Inside Tuchel's final day at Chelsea
Tuchel cleared his desk on Wednesday after the short meeting at 9.30am where he was dismissed and stayed at the training ground with his departing coaching staff to say their goodbyes.
The German manager, who joined the club in January 2021, wants to take a break before returning to football.
Tuchel is still highly regarded by many people at Chelsea because of the trophies and the leadership he showed during extremely difficult circumstances. At Chelsea, the coronavirus pandemic and the end of the Abramovich era were difficult scenarios - the latter resulting in club sanctions, employees not being paid and a fear of the club going out of business.
Tuchel also showed leadership during the takeover saga, while many key figures such as Bruce Buck, Marina Granovskaia, Petr Cech announced their departures.
Clubs such as Manchester United and Barcelona were interested in Tuchel last season but he was always loyal to Chelsea.
Although Chelsea ended up spending a record £278m this summer there were differences of opinion between the co-owners and Tuchel on some targets and strategy.
For example, the owners were open to the idea of signing Cristiano Ronaldo from United but he was not wanted by Tuchel.
Meanwhile, Chelsea co-owners Boehly and Behdad Eghbali met Chelsea players and staff on Wednesday afternoon at Cobham.
They explained what had happened with Tuchel and their vision for the future of the club. Boehly and Eghbali were also at the game in Zagreb on Tuesday.
September 10: Fulham (A) - kick-off 12.30pm
September 14: Red Bull Salzburg (H) - kick-off 8pm
September 18: Liverpool (H) - kick-off 4.30pm
October 1: Crystal Palace (A) - kick-off 3pm
October 5: AC Milan (H) - kick-off 8pm