Nevertheless, the Stamford Bridge giants claim the shirt number is not confirmed for the 2022-23 campaign.
Chelsea has announced that Kalidou Koulibaly will wear jersey 26 for the Blues.
The Senegal international was signed by the Premier League side from Serie A side Napoli in a deal worth £34 million ($41m) as Thomas Tuchel strives to restructure his defence following the exit of Antonio Rudiger and Andreas Christensen.
As the London club continue preparations for the commencement of the new season, they confirmed the shirt number the African and Raheem Sterling would be wearing – although just for pre-season.
“Ahead of our next match on the United States tour, we can confirm the pre-season shirt numbers for our two new signings and a change for another player,” a statement from the club read.
“Raheem Sterling has taken on the 17 shirt for these preparation games while Kalidou Koulibaly will wear 26.
“Conor Gallagher, who wore 38 in our win over Club America at the weekend, has changed to number 15.
“Please note, these pre-season numbers are not confirmed for the season ahead.”
Other players who have worn this iconic jersey number for Chelsea are legendary England captain John Terry, Laurent Charvet, Neil Clement, Michael Duberry and Andy Dow.
In a recent interview, manager Tuchel hoped the 2021 Africa Cup of Nations winner shows his quality as soon as possible while hoping the presence of Edouard Mendy and Jorginho will help him settle quickly.
“He brings experience, top defensive quality, height, and everything we are looking for to play in a back-three or a back-four,” the German told Chelsea website.
“It’s another brilliant signing for us, and we hope Kalidou can show his quality as soon as possible.
“He knows some of the players. He plays with Edouard Mendy with his national team and he played with Jorginho at Napoli.
“I think for this side it will be very quick that he feels welcome in the group. It’s a nice group, and everybody is happy that he is with us now.”
Koulibaly is expected to make his debut when the two-time Champions League winners square up against Charlotte on July 21.