The new deal will keep Gunter at Reading until the summer of 2018.
Gunter’s contract was due to expire at the end of this season.
Royals boss Brian McDermott said: “We are all absolutely delighted that Chris has committed to the club for another two years.
“He was one of the first signings I made after earning promotion to the Premier League here in 2012 and he has gone on to play more than 150 times for our club since.”
