Thomas Tuchel was appointed Chelsea manager on an 18-month contract on Tuesday, tasked with hauling the underperforming Blues back into the Champions League next season.
The 47-year-old German replaces the sacked Frank Lampard to become the 13th Chelsea boss since Russian oligarch Roman Abramovich bought the club in 2003.
"I would like to thank Chelsea FC for their confidence in me and my staff," said Tuchel.
"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 will take charge for the first time when Wolves visit Stamford Bridge in the Premier League on Wednesday.
Lampard, Chelsea's record goalscorer as a player, was dismissed on Monday after a run of five defeats in eight league games that saw his side slide to ninth in the table, 11 points behind leaders Manchester United.
That was not the return Abramovich expected after a £200 million ($300 million) spending spree in the summer transfer window at a time when most of Europe's top clubs were scaling back due to the economic consequences of the coronavirus pandemic.
"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," said Chelsea director Marina Granovskaia.
"There is still much to play for and much to achieve, this season and beyond."
Tuchel's task will be to get the best out of German compatriots Timo Werner and Kai Havertz, who have struggled to live up to their price tags in their first few months in England.
Despite guiding Paris Saint-Germain to their first Champions League final in August, Tuchel was sacked himself by the French champions last month.
His falling out with PSG sporting director Leonardo played a large part in that and his habit of fractious relations with his employers does not bode well for his prospects at a club with such a famously impatient owner.
"Tuchel will be exposed to exactly the same rules as Frank," said Lampard's former England team-mate Gary Neville.
"We'll be talking about him being let go in the next 18 months to two years, I'm pretty sure of that."
Tuchel previously held talks with Chelsea over replacing Antonio Conte after he left Dortmund in 2017.
Instead, he ended up in the French capital, where he won back-to-back league titles and ended PSG's run of crashing out the Champions League in the last 16.
Chelsea face a daunting last-16 tie when the Champions League returns next month against La Liga leaders Atletico Madrid.
Tuchel also has to win round the Chelsea support that have been upset at the handling of Lampard's dismissal.
"Absolutely gutted. Frank Lampard is, and always will be, a legend of Chelsea Football Club," the Chelsea Supporters' Trust tweeted on his departure.
Lampard achieved a fourth-place finish in his first season in charge to secure a place in the Champions League despite a transfer ban and the sale of Eden Hazard to Real Madrid.
However, his Premier League points-per-game average of 1.67 is the lowest for any Chelsea manager in the Abramovich era.
"I am disappointed not to have had the time this season to take the club forward and bring it to the next level," said Lampard.