Brill, 23, made over 100 appearances for his hometown club, including a Johnstone's Paint Trophy win against Scunthorpe at Wembley last season.
Latics boss Dave Penney believes Brill can flourish at Boundary Park and told the club's official website: "Dean was being tipped for the Premier League a couple of years ago.
"His career has stood still a little since but I'm confident he can kick start things here.
"He has the quality and he has the right attitude. Dean is a player who has played at Championship and League One level and at 23 he's the right age to progress and continue getting better.
"I expect Dean and Greg (Fleming) to fight for the number one spot. Our recruitment efforts are ongoing and hopefully we will see more action again soon."