Moriarty and Francis, who can both represent Wales or England, will be joined by fellow newcomers, Bath lock Dominic Day, Cardiff Blues duo Kristian Dacey and Gareth Anscombe and Newport Gwent Dragons backs Tyler Morgan and Jack Dixon.
Uncapped Ospreys pair Rory Thornton and Eli Walker are also included but Gatland's extended squad contains 17 players with World Cup experience.
Prop Gethin Jenkins, aiming to feature in a fourth World Cup, is joined in the party by European Champions Cup winner Leigh Halfpenny and Six Nations squad members Hallam Amos, Alex Cuthbert, George North and Liam Williams.
Clermont Auvergne centre Jonathan Davies, who has played 48 times for Wales, is out after rupturing his anterior cruciate knee ligaments last month.
"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," Gatland said in a news release on Monday.
Gatland will cut the squad to 31 players at the end of August.
Wales, drawn in Group A alongside England, Australia and Fiji, play Uruguay in their opening World Cup match in Cardiff on Sept. 20.
Training squad:
Backs: Gareth Davies (Scarlets), Mike Phillips (Racing Metro), Rhys Webb (Ospreys), Lloyd Williams (Cardiff Blues), Gareth Anscombe (Cardiff Blues), Dan Biggar (Ospreys), James Hook (Gloucester), Matthew Morgan (Bristol), Rhys Patchell (Cardiff Blues), Rhys Priestland (Scarlets), Cory Allen (Cardiff Blues), Jack Dixon (Newport Gwent Dragons), Tyler Morgan (Newport Gwent Dragons), Jamie Roberts (Racing Metro), Scott Williams (Scarlets), Hallam Amos (Newport Gwent Dragons), Alex Cuthbert (Cardiff Blues), Leigh Halfpenny (Toulon), Tom James (Exeter Chiefs), George North (Northampton Saints), Eli Walker (Ospreys), Liam Williams (Scarlets)
Forwards: Rob Evans (Scarlets), Tomas Francis (Exeter Chiefs), Paul James (Bath), Aaron Jarvis (Ospreys), Gethin Jenkins (Cardiff Blues), Rhodri Jones (Scarlets), Samson Lee (Scarlets), Nicky Smith (Ospreys), Scott Baldwin (Ospreys), Kristian Dacey (Cardiff Blues), Richard Hibbard (Gloucester), Ken Owens (Scarlets), Jake Ball (Scarlets), Luke Charteris (Racing Metro), Dominic Day (Bath), Bradley Davies (Wasps), Alun Wyn Jones (Ospreys), Rory Thornton (Ospreys), Dan Baker (Ospreys), Taulupe Faletau (Newport Gwent Dragons), James King (Ospreys), Dan Lydiate (Ospreys), Ross Moriarty (Gloucester), Justin Tipuric (Ospreys), Sam Warburton (captain - Cardiff Blues).
