The 25-year-old made 18 appearances for the Addicks in the second half of last season, helping Lee Bowyer's side win promotion via the League One play-offs.

Midfielder Williams was released in May, but started pre-season with the club and has now agreed a one-year deal with the option of a second.

"I'm delighted to be able to get him back," Bowyer said.

"Jonny has dropped his wage a hell of a lot to come here and I'm grateful to him for doing that.

"I think that just shows how much he enjoyed last season with us."

Williams began his career at Crystal Palace and has also had loan spells at Ipswich Town, Nottingham Forest, MK Dons and Sunderland.