Chelsea have completed the signing of Malang Sang on a five-year deal after the 21-year-old left Nice after the expiration of his contract.
Having been under a transfer ban a year ago, the Blues are making up for lost time by flexing their financial muscle in this window.
Prior to Sarr, they spent £136m on Hakim Ziyech from Ajax, Timo Werner from RB Leipzig, and Ben Chilwell from Leicester.
In addition to those players, and now Sarr, they are still looking at the possibility of signing Kai Havertz from Leverkusen and Jan Oblak from Atletico Madrid.
The Frenchman had been wanted by a number of clubs last season and into this summer when he would be free to talk to anyone after leaving Nice, turning down a new contract last year.
Chelsea announced the signing on Thursday on their official site and social media pages.
“The opportunity to sign Malang was one we could not miss. He is a tremendous prospect and we will be monitoring him closely during his loan period, hoping he will soon be back at Chelsea," Chelsea director Marina Granovskaia said.
“We are very happy to welcome him to the club today."
The London side have confirmed that Sarr will be loaned out to another club for the duration of the 2020/21 campaign.