The 32-year-old Norway international's contract was not due to expire until the end of next season but it has been confirmed that he will not remain with the club as they adapt to life in the Championship.
Hangeland was brought to Craven Cottage by current England manager Roy Hodgson in 2008, helping Fulham to avoid relegation on goal difference at the end of a thrilling 2007-08 campaign.
The American-born defender would go on to become an integral part of the first team and featured heavily as the Cottagers reached the final of the 2010 Europa League - losing 2-1 to Atletico Madrid after extra time.
A short statement on the club's official website read: "The club would like to thank Brede for his six-and-a-half years of committed service and wishes him the very best in all of his future endeavours."
Hangeland made 272 appearances for Fulham, scoring 12 goals.
A string of experienced players have already departed Craven Cottage following their relegation, including Steve Sidwell, Damien Duff and John Heitinga.