Thomas Tuchel has been appointed as the new head coach of Chelsea.
The German was confirmed on Tuesday as the successor to Frank Lampard, who was sacked on Monday. The club said Tuchel had signed an 18-month contract "with the possibility of an extension".
Chelsea also confirmed that Tuchel would take charge of his first training session on Tuesday evening and will be in the Stamford Bridge dugout for Wednesday's Premier League clash with Wolves.
"I would like to thank Chelsea FC for their confidence in me and my staff," Tuchel told the club website.
"We all have the greatest respect for Frank Lampard's work and the legacy he created at Chelsea. At the same time, I cannot wait to meet my new team and compete in the most exciting league in football.
"I am grateful to now be part of the Chelsea family - it feels amazing!"
Tuchel was available after his departure from Paris Saint-Germain, where he won back-to-back Ligue 1 titles and reached last season's Champions League final before being replaced by ex-Tottenham boss Mauricio Pochettino.
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The 47-year-old began his managerial career in Germany, going on to win the German Cup in 2017 with Borussia Dortmund, where he spent two years in charge following spells with Augsburg and Mainz.
Chelsea director Marina Granovskaia added: "It is never easy to change head coach in the middle of the season but we are very happy to secure one of Europe's best coaches in Thomas Tuchel.
"There is still much to play for and much to achieve, this season and beyond. We welcome Thomas to the club."
Lampard, who is Chelsea's all-time leading goalscorer, took the Blues to the FA Cup final and secured qualification for the Champions League in what was deemed a largely successful first campaign in charge at Stamford Bridge.
But after spending more than £200m on new players in the summer, Chelsea find themselves in midtable in the Premier League and in danger of missing out on qualification for next season's Champions League.
'Tuchel's dream has become reality; Relationships key'
Sky Sports News' Kaveh Solhekol on The Transfer Show:
"Quite a few of the Chelsea players had issues with Frank Lampard and were unhappy, well there's a new man in charge, there's a new regime and they are going to have to get used to doing things Thomas Tuchel's way.
Obviously, there's been a lot written about Tuchel, what a great coach he is and what a visionary he is. We've read all the words but let's see how good he is in the Premier League. It's been his dream to manage in England and his dream has become reality.
"He's been used to operating in a similar situation to the one he's going to have at Chelsea. He had the same at PSG. He's not going to call the shots when it comes to transfer strategy. There were people above him doing that at PSG. There are people above him doing it at Chelsea. Obviously, he will have an input and Chelsea will look at it, but they will also have their own targets. It's going to be consensual, but he is used to that.
"There are three main areas where he's going to have to manage his relationships.
"The first one is with the fans and I think that's going to be quite easy for him at the moment because there are no fans in the stadium.
"What would it be like if he was stepping out as the Chelsea boss on Wednesday at a packed Stamford Bridge having just taken over from a club legend like Frank Lampard, who many fans think should still be the Chelsea manager. Tuchel is lucky that Stamford Bridge is going to be empty.
"Then there's his relationship with the players. That's obviously going to be key. When he walks into that training ground and meets those players for the first time, some of those players already know him, but they are going to have a lot of respect for him because of what he's already achieved, his coaching pedigree, the fact he got to the Champions League final last season and the fact he's coached players like Neymar and Kylian Mbappe.
"The third, and most important area always at Chelsea, is how you manage your relationships upwards. What is his relationship going to be like with Marina Granovskaia? What is his relationship going to be like with Petr Cech? What is his relationship going to be like with Bruce Buck? Ultimately, what is his relationship going to be like with Roman Abramovich? It's going to be key for Thomas Tuchel.
"Looking at his history and bearing in mind what a political club Chelsea is, his relationships with the people upstairs at PSG weren't great. He had problems in his relationships with the people at Borussia Dortmund as well. Even at Mainz he had some issues."
Gary Neville told Sky Sports News:
"He's managed at big clubs and he's got a lot of experience. He knows a few of the players who are currently at Chelsea. It's another top manager who is coming into the Premier League.
"We've been blessed over the past few years with some absolutely outstanding managers to see the league rise to being the best in Europe again with the performances of clubs in the Champions League improving, with Pep Guardiola, Jurgen Klopp and Mauricio Pochettino getting to semi-finals and finals.
"Tuchel is another manager who has got that sort of pedigree, so it's a great addition to the Premier League if he does come.
"It's Chelsea, and that's what Chelsea do. Frank is not a victim of his poor performance as a manager, he's just someone who's been exposed to Chelsea's model of releasing and employing managers every 12 to 18 months if things don't go as well as they want. That's a pretty high standard that they live to.
"Tuchel will be exposed to exactly the same rules as Frank. We'll be talking about him being let go in the next 18 months to two years, I'm pretty sure of that."
Sky Sports' Nick Wright:
Of the various factors that contributed to Frank Lampard's demise at Chelsea, his inability to get the best out of Timo Werner and Kai Havertz will go down as one of the biggest.
In 35 Premier League appearances between them under Lampard, they provided just five goals and six assists, their struggles intensifying as the season wore on. Werner has not scored a Premier League goal since November, while Havertz's barren spell goes back even further.
While Lampard's managerial philosophy remains fuzzy, even after 18 months in charge of Chelsea, Tuchel's could hardly be clearer. The 47-year-old is a disciple of Jurgen Klopp, having succeeded him both at Mainz and at Borussia Dortmund where he adopted similar high-intensity, high-pressing tactics with an emphasis on speed and efficiency.
"I prefer certain qualities," he once said. "An active playing style, bold defending and pacey play in attack."
Tuchel struggled to instil those principles among the superstars at Paris Saint-Germain but Roman Abramovich has long craved an offensive playing style that provides entertainment as well as results. The German will be tasked with putting that in place at Stamford Bridge.
He must do it by putting Werner and Havertz at the centre of his plans.
Sky Sports' Ron Walker:
While it was a Blue Monday for Lampard this week, Tuchel takes over at Stamford Bridge less than a month after his own sacking as PSG boss, on the back of a fractured relationship with the club's board and the big spenders sitting third in Ligue 1.
The German has honed a strong CV since getting his first break in management when succeeding a young Jurgen Klopp at Mainz in 2009. He has since gone on to re-establish Borussia Dortmund in the Bundesliga before winning back-to-back Ligue 1 titles with PSG, as well as leading the club to its first Champions League final, albeit during a tenure of mixed fortunes in Paris.
Tuchel has long dreamt of a move to the Premier League and has nurtured a reputation for being tactically astute and developing players, but could the 47-year-old's history of fall-outs with his previous clubs' hierarchies - something not unusual at Stamford Bridge - be a worry before he even starts his new role?
Soccer Saturday pundit Paul Merson told Sky Sports News:
"So, Thomas Tuchel is coming in. You've got to remember that he could not control the players at Paris Saint-Germain. The likes of Neymar and Kylian Mbappe did what they wanted. They just played.
"You can't say that this guy is going to come in and just sort the players out at Chelsea. Can he get Havertz playing? Can he get Werner and [Hakim] Ziyech playing? He didn't do it with the players at PSG. It's not like he's coming in and you think, 'he's going to scare these players'.
"I watched PSG a few times under him. They didn't track back, and I didn't see much of a plan.
"Tuchel has got a nice two games coming up. They've just beat Luton and Tammy Abraham has a bit of confidence behind him after scoring a hat-trick. They've got Wolves and Burnley coming up and if you beat them, all of a sudden you move up the table and it is a different game.
"It's all about confidence. Tuchel has got to get the team he wants at Chelsea, and I think he'll get that because he's got time.
"He's not coming to Stamford Bridge for five games. Within two weeks he'll have his best XI and he'll stick with it for four or five games. He won't start chopping and changing. Coming in, he'll know his best XI and that's the difference.
"He's got time now and he'll know he needs to get a settled team as quickly as possible because if he doesn't, it'll be the same old story."