Ospreys second-row Thornton, who has previously trained with the senior national side, will link up with the squad following the conclusion of his under-20 commitments in Italy.
Thornton is joined in the 47-man group by 24 other players with previous under-20 experience, two of them winning the U20 Championship with different countries – Gareth Anscombe (New Zealand in 2011) and Ross Moriarty (in England 2013 and 2014).
Thank you all for your kind messages really proud to be named in the @WelshRugbyUnion squad looking forward to the hard work to come
— Ross Moriarty (@RossMoriarty6)
June 1, 2015
Meanwhile, Gethin Jenkins will be aiming to feature in a fourth Rugby World Cup for his country and is named as one of eight props along with Scarlets trio Rob Evans, Rhodri Jones and Samson Lee, Ospreys pair Nicky Smith and Aaron Jarvis, Paul James and the uncapped Tomas Francis.
Jenkins featured in the 2003, 2007 and 2011 editions of rugby's showpiece event and has played in more Rugby World Cup matches (15) than any other Wales player.
Richard Hibbard, Ken Owens, Scott Baldwin and Kristian Dacey are the four hookers, while Wales' second row contingent from the RBS 6 Nations, Alun Wyn Jones, Jake Ball, Luke Charteris and Bradley Davies are all included along with the uncapped pair of Thornton and Bath lock Dominic Day.
Captain Sam Warburton, Dan Lydiate and Taulupe Faletau who all featured at RWC 2011 are included along with Ospreys trio James King, Dan Baker and Justin Tipuric as well as uncapped Gloucester flanker Moriarty.
There are four uncapped players included in the backs with Anscombe, Newport Gwent Dragons pair Jack Dixon and Tyler Morgan and Ospreys wing Eli Walker all named. Morgan was due to have played in the World Rugby U20 Championship but was withdrawn last week after a knee injury ruled Jonathan Davies out of RWC 2015.
At scrum-half, Six Nations squad members Gareth Davies, Mike Phillips and Rhys Webb are joined by the recalled Lloyd Williams.
Elsewhere, Dan Biggar, Rhys Priestland, Rhys Patchell, James Hook and Matthew Morgan are chosen at fly-half along with centres Jamie Roberts, Scott Williams and Cory Allen.
European Rugby Champions Cup winner Leigh Halfpenny, Six Nations squad members Hallam Amos, Alex Cuthbert, George North and Liam Williams and Cardiff Blues-bound wing, Tom James, form the back three contingent.
The hard work starts here - Gatland
"As a coaching team we are extremely happy with the blend of the squad in terms of the experience we are able to include as well as the young talent that has really impressed us," said Wales coach Warren Gatland.
"The easy part for the players has been done in terms of being selected, the hard work will begin from day one with a huge schedule of preparation ahead of them.
"The players will face a tough couple of months of intensive training, we will be taking them to Switzerland, Qatar and Poland and I can assure everyone they are no holiday camps.
"We put a lot of emphasis on conditioning and preparation in 2011 which worked well for us and we are looking to step that up again this time."
"We put a lot of emphasis on conditioning and preparation in 2011 which worked well for us and we are looking to step that up again this time.
"The 47 players all have the opportunity to make that 31-man party and I'm sure they will all be eager to feature in a World Cup on these shores.
"We believe the longer we are together the better we perform and this summer of preparation will give us every opportunity to be at our best come Rugby World Cup."
The players will embark on an intensive preparation regime over the coming months, including training camps in Switzerland, Qatar and Spala, before Gatland and his fellow selectors whittle down the squad to the 31 players who will contest Rugby World Cup 2015 on 31 August.
Wales will then play their final warm-up match - having already faced Ireland home and away - against Italy at the Millennium Stadium on 5 September.
WALES RWC 2015 TRAINING SQUAD:
Forwards: Rob Evans, Tomas Francis, Paul James, Aaron Jarvis, Gethin Jenkins, Rhodri Jones, Samson Lee, Nicky Smith, Scott Baldwin, Kristian Dacey, Richard Hibbard, Ken Owens, Jake Ball, Luke Charteris, Dominic Day, Bradley Davies, Alun Wyn Jones, Rory Thornton, Dan Baker, Taulupe Faletau, James King, Dan Lydiate, Ross Moriarty, Justin Tipuric, Sam Warburton (captain).
Backs: Gareth Davies, Mike Phillips, Rhys Webb, Lloyd Williams, Gareth Anscombe, Dan Biggar, James Hook, Matthew Morgan, Rhys Patchell, Rhys Priestland, Cory Allen, Jack Dixon, Tyler Morgan, Jamie Roberts, Scott Williams, Hallam Amos, Alex Cuthbert, Leigh Halfpenny, Tom James, George North, Eli Walker, Liam Williams.
