Carlos Edwards, Ed Upson, Lee Martin and John Marquis are among the players told they will not be offered deals.
Three under-21 players - Jack Powell, Chris Parr and Keaton Wood - are also being released by the Lions.
Mark Beevers is in talks over a new deal while defenders Byron Webster and Joe Martin have activated one-year extension clauses in their contracts.
The Lions missed out on promotion to the Championship after a 3-1 defeat by Barnsley at Wembley.
Millwall have confirmed seven players will leave the club following Sunday's League One play-off final defeat.