The England international previously spent half-a-season with Palace on loan from Chelsea, joining for the latter stages of 2024/25 – and ending his spell in style by helping the Eagles lift the FA Cup trophy at Wembley.
Having spent last season with RC Strasbourg – where he played against Palace in the UEFA Conference League, among his 34 appearances – Chilwell has now returned to the club.
The 29-year-old began his senior career with Leicester City, where he made 123 appearances over five years, before moving to Stamford Bridge in August 2020, where he lifted both the UEFA Champions League and UEFA Super Cup.
He subsequently moved to Palace and played 11 times, scoring once, en route to winning his – and the club's – first domestic trophy at Wembley.
A full England international, Chilwell has also won 21 caps for the Three Lions, scoring once. He was part of the England team which reached the Euro 2020 final.
Chilwell becomes Palace’s ninth signing of the summer, after Óscar Mingueza, Takehiro Tomiyasu, Dwight McNeil, Evann Guessand, Anan Khalaili, Zavier Gozo, Axel Disasi and Honest Ahanor.
Chairman Steve Parish said: “With his experience and quality, Ben played a huge part in us winning our first trophy last year.
“It is terrific to welcome him back to Crystal Palace. We hope he can help us to further success.”
Chilwell said: “It's amazing to be back. It's nice to see some familiar faces, and I'm just really excited to get back in, see the boys and the fans – and get going again."