Millwall quartet Shane Lowry, Andy Keogh, Liam Feeney and Jack Smith have been released by the club.
All four players will become free agents when their contracts expire next month after being told by Lions boss Ian Holloway that their futures lie away from The Den.
Simeon Jackson is also unlikely to return to the club when his short-term deal runs out.
However, fellow striker Jermaine Easter has signed a new one-year contract with the Sky Bet Championship club.
Millwall have also announced that they hope to retain Lee Martin and David Forde, with the duo set to discuss terms in the near future.