Ken Owens was ruled out because of a back injury, forcing coach Warren Gatland to pick a new captain for the tournament in France starting September 8.
Gatland has chosen to go with two captains.Â
The 23-year-old Morgan isn't a surprise, having led the Welsh in their most recent warm-up game - a 52-16 loss to South Africa on Saturday.
Wales, who have reached the semi-finals in two of the past three World Cups, is in the same pool as Fiji, Portugal, Australia and Georgia.
The team's opening game is against Fiji in Bordeaux on September 10.
Seventeen of the squad have previous World Cup experience, with centre George North set to appear in the tournament for the fourth time.
Loosehead prop Corey Domachowski and tighthead Henry Thomas won their first senior caps for Wales this month.
No. 8 Taulupe Faletau and flyhalf Gareth Anscombe were picked despite being injury concerns.
"The toughest part of the job is always selection and this is particularly the case when it comes to picking a World Cup squad," Gatland said.
WALES RUGBY WORLD CUP SQUAD
Forwards: Taine Basham, Adam Beard, Elliot Dee, Corey Domachowski, Ryan Elias, Taulupe Faletau, Tomas Francis, Dafydd Jenkins, Dewi Lake (co-captain), Dylan Lewis, Dan Lydiate, Jac Morgan (co-captain), Tommy Reffell, Will Rowlands, Nicky Smith, Gareth Thomas, Henry Thomas, Christ Tshiunza, Aaron Wainwright.
Backs: Josh Adams, Gareth Anscombe, Dan Biggar, Sam Costelow, Gareth Davies, Rio Dyer, Mason Grady, Leigh Halfpenny, George North, Louis Rees-Zammit, Nick Tompkins, Johnny Williams, Liam Williams, Tomos Williams.
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