The 28-year-old, who can operate in a number of positions on the left side of the pitch, joins the Eagles until the end of the season.
Chilwell’s first taste of senior football came with Leicester City, having joined their Academy aged 12. He made his full debut in October 2015, before joining Huddersfield Town a month later for a short-term loan in the Championship.
The attacking full-back became a first-team regular at the Foxes the following season and would go on to make 123 appearances for Leicester across a five-year spell, prior to joining Chelsea in August 2020.
During his time at Stamford Bridge, the defender has won both the UEFA Champions League and UEFA Super Cup.
Chilwell also made his senior international debut for England in 2018 at the King Power Stadium, during a 1-0 win over Switzerland. He has won 21 caps for the Three Lions to date, scoring his first goal for the team against Andorra in October 2021, and was part of the England squad which reached the Euro 2020 final at Wembley.
He becomes Palace’s second signing of the January transfer window, following the arrival of Romain Esse.
Chilwell said: “I'm very excited to be here. Crystal Palace are a club that's going in a great direction. You look at the last few months, with the results and how the team's playing, and it was a no-brainer to make the decision to come here."
Chairman Steve Parish said: “Ben has experience at the highest level of European and international football. I’m delighted that he has joined us on loan, and we believe he will prove to be a great addition to the squad.”