Rhys Patchell's superb second-half, try-scoring performance in Saturday's 22-17 defeat to Ireland has seen the fly-half rewarded with a place in Wales' Rugby World Cup 2019 squad, meaning Jarrod Evans, the man he replaced at half-time at the Principality Stadium, misses out.
Meanwhile, Rhys Carre has also been included less than 24 hours after making his test debut. The 21-year-old prop, who has signed for English Premiership champions Saracens, started Saturday's match and has edged out the experienced Rob Evans for a place in the touring party.
Gatland, who will step down as Wales head coach following the tournament, has also included second-row Cory Hill despite confirming on Saturday that a leg injury would “keep him out until game two or three”.
Wales kick off their Pool D campaign against Georgia in Toyota on 23 September, and play Australia in Tokyo six days later before facing Fiji on 9 October in Oita and Uruguay in Kumamoto four days after that.
Meanwhile, captain Alun Wyn Jones will feature at a fourth Rugby World Cup. Jones is one of 11 survivors from the squad that defeated hosts England at Twickenham four years ago before being beaten in the quarter-finals by South Africa at the same stadium.
The Ospreys second-row - the most-capped Welshman in history - made his Rugby World Cup debut during his country’s pool stage exit at France 2007 and travels to Japan having made 15 tournament appearances.
Jones is one of five players included who were part of the Wales squad that finished fourth at New Zealand 2011. Hooker Ken Owens and winger George North will appear at a third Rugby World Cup later this month, while Jonathan Davies - named alongside brother James on Sunday - and Leigh Halfpenny were both injured for England 2015.
Gatland has elected for an 18-13 split between forwards and backs and has opted to take three hookers and as many scrum-haves on the trip to Japan.
"Toughest part of the job"
“Selection is always the toughest part of the job and that is especially true come RWC time,” Gatland said.
“Reducing the squad down to 31 has been extremely hard especially when you look at the depth we have created and the amount of the work the training squad have put in, for some, 14 weeks of training.
“We are really happy with the final 31, we feel there is an excellent blend to the squad, in terms of talent, experience and age profile and we are all incredibly excited about heading to Japan and what lies ahead.
“These players have performed and delivered for Wales and deserve the opportunity to represent their nation at the game’s showpiece tournament.”
Wales round off their preparations for Japan 2019 with a fourth and final warm-up match against Ireland at the Aviva Stadium in Dublin next weekend.
The country’s best Rugby World Cup performance remains their third-place showing at the inaugural competition in 1987, however, they head to Japan 2019 full of confidence having briefly enjoyed a stay at the top of the World Rugby Men's Rankings.
Wales Rugby World Cup 2019 squad:
Forwards: Jake Ball, Adam Beard, Rhys Carre, James Davies, Elliot Dee, Ryan Elias, Tomas Francis, Cory Hill, Alun Wyn Jones, Wyn Jones, Dillon Lewis, Ross Moriarty, Josh Navidi, Ken Owens, Aaron Shingler, Nicky Smith, Justin Tipuric, Aaron Wainwright.
Backs: Josh Adams, Hallam Amos, Dan Biggar, Aled Davies, Gareth Davies, Jonathan Davies, Leigh Halfpenny, George North, Hadleigh Parkes, Rhys Patchell, Owen Watkin, Tomos Williams, Liam Williams.