Ream joined the Cottagers from Bolton in August 2015 and went on to make 312 appearances in all competitions for the London team.
"When I walked through the Motspur Park doors in 2015, I would have never predicted what the following nine years would bring," Ream told Fulham's website.
"The memories made, the connections formed, and the people met along the way have made my time at Fulham more than special.
"I wish I could thank everyone individually for the part they played in shaping me as a player, but more as a person. For all of that, I am beyond grateful. As of today I am no longer a player, but I will always be a fan of Fulham Football Club."
Fulham, who finished 13th in the Premier League last season, begin the new campaign away to Manchester United on August 16.
