Former England defender Jonathan Woodgate is among the senior players to be released by Middlesbrough following their promotion to the Premier League.
Woodgate, 36, was part of the squad that secured a return to the top flight this season but made only one appearance in the League Cup.
The centre-half played 112 games during two spells with his home-town club.
Defender Damia Abella has also exited having played seven times, while Rhys Williams has moved to Perth Glory.
Goalkeeper Luke Coddington has joined Huddersfield Town, while Jordan Jones and Andre Bennett have also departed.
Loanees Tomas Kalas, Gaston Ramirez, Ritchie de Laet, Kike Sola and Michael Agazzi have returned to their parent clubs.