Wigan defender Antolin Alcaraz scored with a header three minutes from time to end Blackburn's 11-year stay in the Premier League after a dismal season in which they have won just eight of their 37 league matches under manager Steve Kean.
Rovers, champions in 1995, joined Wolverhampton Wanderers in dropping to the championship as Wigan climbed to 15th in the standings, securing their top-flight status with one game left following a superb late run including wins over champions Manchester United and Arsenal.
"It doesn't seem real yet," Wigan manager Roberto Martinez told Sky Sports. "Is a great feeling. It was a difficult game, you could feel the tension and it was a cagey affair. But staying up is an incredible achievement."
Bolton Wanderers or Queens Park Rangers will join Wolves and Blackburn in the championship next season.
Bolton, two points behind QPR, must beat Stoke City on Sunday to have any chance of survival and Rangers need a point at Premier League leaders Manchester City to guarantee staying up.
