David Luiz has signed a three-year deal to rejoin the Blues from Paris Saint-Germain.
The £32million transfer means the Blues, who sold him to the Paris side for £50million in 2014, have made a tidy £18million profit.
Chelsea have been in panic mode in the past weeks as they have seen a succession of deals fall through due to what head coach Antonio Conte called a "crazy' transfer window.
The price for all their original targets doubled s soon as their interest became official.
With Chelsea, a centre-back short, there were plenty of options, but Luiz, who was no longer a certain starter for PSG the last throw of the die by the Chelsea hierarchy.
But he's back.
The centre-back, 29, said: "I'm delighted to return to Chelsea. We had a fantastic story during my first time at the club and I want to help the team and Antonio Conte achieve a lot of success.
"I always had a wonderful relationship with the fans and I am looking forward to wearing the blue shirt at Stamford Bridge once again."
Luiz will fight John Terry and Gary Cahill for a starting line-up in the next match after the international break at Swansea City on Sunday week.
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