Charlton have signed goalkeeper John Sullivan on a free transfer following his release by London rivals Millwall.
The 23-year-old, who finished the season on loan at The Valley, has signed a two-year deal.
Addicks boss Chris Powell told the club's official website: "He impressed me. I spoke to the people at Millwall and he surpassed what I thought he would bring.
"He's very vocal around the training ground and is a good character around the dressing room.
"He demands a lot from the players around him and from himself."