Watford captain Manuel Almunia heads a list of several experienced players who are set to be released by the club.
Goalkeeper Almunia will leave the Sky Bet Championship club when his contract expires at the end of June, along with Marco Cassetti, Ross Jenkins and Nyron Nosworthy.
The short-term deals of Fitz Hall, Lucas Neill and Albert Riera all expire this summer and they will also depart Vicarage Road.
Technical director Gian Luca Nani told the club's official website: "Our thanks go to all the players whose contracts finish this summer.
"They have helped create some great moments over the last few years that everyone connected with the club will remember fondly.
"Nyron Nosworthy has been a fantastic professional, while Ross Jenkins has come through the club's Academy and made over 90 appearances for the first-team. Gary Woods has provided great competition to the goalkeepers at the club.
"Fitz Hall, Lucas Neill and Albert Riera have all assisted the squad with their experience at crucial times.
"Special mention should go to captain Manuel Almunia for his true professionalism and to Marco Cassetti for embracing the club after moving from Italy.
"We wish all the players every success for the future, both professionally and in their private lives."
Third-choice goalkeeper Gary Woods' contract is due to run out, although the club remains in talks with the player's representatives.
Defender Lloyd Doyley and midfielder Luke O'Nien have already signed contract extensions.