The 30-year-old shot-stopper joins the club on loan until the end of the 2024/25 season.
Capped 44 times by the United States, Turner is an experienced goalkeeper whose accomplished career has spanned spells in the MLS and Premier League.
Turner’s breakthrough came during six years with New England Revolution, where he made 111 appearances and – in 2020 – was voted Revolution Player of the Year. The following year, he was selected to play in the MLS All-Star Game after being named Goalkeeper of the Year in the MLS Best XI.
In 2022, Turner moved to Arsenal, where he kept four clean sheets in seven appearances. He featured more regularly at Forest last season, playing 21 times.
Turner also possesses an impressive record in major tournaments, being named Goalkeeper of the Tournament in the successful 2021 CONCACAF Gold Cup campaign after keeping five clean sheets in six matches. He has also twice won the Nations League with his country.
Turner said upon joining: "I'm really excited to be here – and I'm ready to get to work.
"I've heard a lot about [goalkeeping coach] Dean Kiely from Wayne Hennessey, and obviously Dean [Henderson] and Remi [Matthews] have got a lot of experience, so it'll be great to get to know them, learn how they work, support them in whatever ways I can, but also push them to be the best versions of themselves."
Chairman Steve Parish said of Turner’s arrival: “It is vitally important in any squad to have competition for places, and Matt – with his experience of the Premier League and at international level – represents an excellent addition to our goalkeeping ranks this season. We look forward to working with him at Palace.”