Ben Hamer has left Reading to sign a three-year deal with Charlton for an undisclosed fee as the club's 14th signing this summer.
Addicks manager Chris Powell welcomed the 23-year-old goalkeeper to The Valley after a hectic summer in the transfer market.
"When I heard about the interest from Charlton I was very excited," Hamer told the club's official website.
"The Valley is a big stadium and it's a club with a big fanbase, a club that has the potential to push on, so I'm delighted to come on board.
"I've seen all the signings this summer and it's clear the club is looking to push for promotion this year, and I want to help Charlton get into the Championship."
Hamer made just five appearances for Reading but impressed on loan spells with Brentford and Exeter.