Southampton came from behind to extend their unbeaten home record to 12 games. Rickie Lambert's hat-trick sealed the three points which keeps Saints second in the Championship table.
It was the visitors to St Mary's who started brightly, and Forest went ahead when Matt Derbyshire prodded the ball home from close range. Saints responded moments later however, when Lambert grabbed his first goal - scoring on the rebound after Lee Camp had stopped David Connolly's shot.
Saints then forced themselves in front as Lambert headed home from close range after Adam Lallana flicked a good ball on.
Forest had the final say in a pulsating first half as Derbyshire set up Radoslaw Majewski for an easy finish to tie up the game.
Southampton came out positively in the second half, but they had to wait until the final ten minutes to find the winning goal. Danny Fox's perfect ball in was met by a powerful header from Lambert who sealed his hat-trick and the important three points for Saints.
Saints rode their luck at times, but will be more than happy with a big win - their first over Forest since 1997. Next for Nigel Atkins' side is a trip to Birmingham, where a win could turn Saints into true promotion candidates.