They join the three who have already left, laying bare the scale of the rebuilding job being undertaken by Danny Wilson, the club’s head coach.
Amongst those heading for the exit door are former Scotland winger Lee Jones, Irish international stand-off Ian Keatley and loosehead prop Aki Seiuli.
It was already known that experienced internationals Adam Hastings, Huw Jones, Leone Nakarawa and Niko Matawalu were moving on.
“We’d like to thank all of our leavers for what they have done as Warriors this season,” Wilson told glasgowwarriors.org.
“Their contributions both on and off the field cannot be understated and we wish them all the best for the future.”
Glasgow have already announced a number of new signings for next season, including Lewis Bean, Simon Berghan, Jamie Bhatti, Sebastian Cancelliere, Jack Dempsey, Josh McKay, Ally Miller, Domingo Miotti, Sione Tuipulotu, Duncan Weir. In addition, Rory Darge has already joined the club from Edinburgh.
The 21 leavers are:
Alex Allan (109 appearances)
Scotland loosehead departs after seven years at Glasgow Warriors having helped the club to the Guinness PRO12 title in 2015.
Glenn Bryce (33)
The full-back Bryce left in January to join US Major League Rugby side LA Giltinis.
Mesu Dolokoto (3)
Fijian international hooker scored two tries on his debut against Zebre in February 2020 but used sparingly.
Dylan Evans (7)
Loosehead departs after short-term loan from the Scarlets.
Chris Fusaro (183)
Announced his retirement earlier this month. Third most appearances in Glasgow Warriors’ history.
Adam Hastings (52)
Scotland stand-off is joining Gloucester.
TJ Ioane (13)
Joined from London Irish ahead of the 2020-21 season.
Huw Jones (49)
Scotland outside centre expected to move to France.
Lee Jones (92)
Stalwart winger Jones, 30, moves on after seven years, 92 appearances and 18 tries for Glasgow.
Ian Keatley (4)
Irish international stand-off leaves after short-term deal.
Paddy Kelly (6)
Inverness-born centre Kelly was part of Great Britain 7s programme earlier this year.
Fotu Lokotui (13)
Flanker will join French side Agen next season.
Niko Matawalu (138)
Fans’ favourite moves on at the end of his second stint at Scotstoun. The club’s third highest try scorer behind DTH van der Merwe and Tommy Seymour.
Robbie Nairn (12)
Former Scotland U20 winger Nairn scored three tries in his 12 appearances.
Leone Nakarawa (80)
Another in his second spell at the Warriors. Set to join Ulster.
Adam Nicol (18)
Tighthead will move to Jersey Reds this summer, after playing there on loan.
D’arcy Rae (86)
Scotland international prop will join Bath after seven years at Glasgow.
Aki Seiuli (28)
Samoan loosehead Seiuli was nominated for the club’s player of the Season in 2019/20.
Tommy Seymour (150)
Outstanding servant announced his retirement earlier this month. Scored 48 tries in Glasgow colours in a career that also included 20 tries in 55 Scotland caps. Top try-scorer on 2017 British and Irish Lions tour.
Brandon Thomson (31)
Fly-half left in February to join Cheetahs in his native South Africa.
George Thornton (2)
Former Scotland U20 prop.