The 24-year-old, who can play in central defence or right-back, has signed a two-year contract.
He was originally signed by Richie Barker in July 2012 and went on to make 80 appearances for Reds in League One over the next two seasons, scoring three goals.
Mark moved on in July 2014 and signed for Scottish Premier League side Kilmarnock. He was made captain at Rugby Park and played 39 times for the club, although his appearances were restricted by injury last season.
Bolton Wanderers paid £1million to Wolves for him in 2009.
Head coach Dermot Drummy said: “We have been looking for an aggressive, dominant defender to complement what we already have and I think we have found him in Mark.
“He’s a warrior and he’s also a very good defender who can play centrally or at right back.
“I like the versatility he offers. Speaking to people at the club, I know how popular he was during his first spell here and I’m delighted for everyone that we’ve been able to bring him back.”
Now fully fit, the club have beaten off competition from four other clubs to bring back a player who was one of the most popular in the squad during his first spell with Reds.
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