Millwall have begun preparations for League One football next season by releasing 18 players, including long-serving defender Alan Dunne.
The 32-year-old made a total of 388 appearances for the Lions after breaking through the club's youth ranks, scoring 23 goals during that time.
Chairman John Berylson paid tribute to the outgoing fan favourite, telling the South London outfit's official website: "It is always sad when a member of your family who has lived with you for a long time leaves home.
"He has written his own chapter in Millwall's history and he will always be very welcome whenever he returns. While Alan will continue his playing career elsewhere, it would not surprise me to see him back here in some capacity further down the line."
Carlos Edwards, Ricardo Fuller, Danny Shittu and Martyn Woolford are among the other 17 players to have been cut loose by Millwall, while Jimmy Abdou and John Marquis will be offered new deals at The Den.
Other squad members to have been deemed surplus to requirements include Nicky Bailey, Matthew Briggs, Richard Chaplow, Magaye Gueye, Justin Hoyte, Stefan Maierhofer and Angel Martinez.
Young prospects Dylan Casey, Sofiane El-Bekri, Denzel Gerrar, Jake Goodman, Josh Siafa and Callum Webb have also been shown the door following the Lions' relegation from the Championship.