Fisher had led the Titans for 17 seasons and had been the longest tenured coach working in the National Football League. The announcement did not indicate whether Fisher had resigned or was fired.
A news conference was expected Friday to provide more details.
The announcement was surprising, since franchise owner Bud Adams had said this month Fisher would be back to coach the team despite a 6-10 record -- Tennessee's first losing mark in six years. The Titans lost eight of their last nine games and quarterback Vince Young was cut after the season.
"The results of his leadership have been some very good football teams and I believe he will get us back to an elite level," Adams said when he announced Fisher was staying.
Fisher, who had one year left on his contract, coached the Titans to a 147-126 record. They won the AFC South title as recently as two years ago and in 1999 reached the Super Bowl before losing to St. Louis.
Fisher's departure leaves Andy Reid of Philadelphia with the longest current tenure with one team. Reid has been with the Eagles for 12 seasons.
Washington's Mike Shanahan has coached for 17 NFL seasons, but with three teams.