Chelsea signed France defender Maxence Lacroix from Crystal Palace in a deal worth a reported £52 million ($69 million) on Thursday.
Lacroix agreed a six-year contract with the Blues and will link up with his new club for their pre-season preparations.
The 26-year-old has won seven caps for France and played for his country at the recent World Cup.
"I am really happy to be part of this beautiful club. Everyone knows the legend of Chelsea, its tradition of winning, and to be a part of that is a proud moment," Lacroix said.
"When I spoke with the manager, I saw that we have the same direction and desire for this club.
"We want to win. When you see the quality of the players here, everything we have around the club, it's something that we can achieve. The ambition is to lift trophies, and I can't wait to contribute."
Lacroix made 98 appearances for Palace after arriving from Wolfsburg in 2024.
The talk of the town. 📻 pic.twitter.com/Eix5531jhy
— Chelsea FC (@ChelseaFC) July 30, 2026
He won the FA Cup, the UEFA Conference League and the Community Shield during his time at Selhurst Park.
Lacroix is the latest close-season signing for new Chelsea boss Xabi Alonso after the British record £117 million swoop for Aston Villa forward Morgan Rogers and a £47 million move for Atalanta right-back Marco Palestra.
Geovany Quenda and Emmanuel Emegha have joined Chelsea in transfers that were initially agreed in 2025.
The Blues have also been linked with Brighton striker Danny Welbeck and Brentford midfielder Jordan Henderson.
Alonso, who took charge on July 1, is looking to revitalise a Chelsea side that finished a disappointing 10th in the Premier League last season, failing to qualify for European action in the coming campaign.