The inclusion of Josh Adams is one of three changes to the Wales side that will face the Wallabies at the Millennium Stadium on Saturday.
Adams, lock Adam Beard and tighthead prop Tomas Francis have been selected in the run-on side, replacing Luke Morgan, Cory Hill and Dillon Lewis.
Dan Biggar is back and available for selection, but there is no place for him in the starting team as Gatland has opted to persist with Gareth Anscombe at No 10.
Biggar is joined by scrumhalf Tomos Williams and utility back Liam Williams as the new additions to the match 23.
Wales – 15 Leigh Halfpenny, 14 George North, 13 Jonathan Davies, 12 Hadleigh Parkes, 11 Josh Adams, 10 Gareth Anscombe, 9 Gareth Davies, 8 Ross Moriarty, 7 Justin Tipuric, 6 Dan Lydiate, 5 Alun Wyn Jones (c), 4 Adam Beard, 3 Tomas Francis, 2 Ken Owens, 1 Nicky Smith.
Subs: 16 Elliot Dee, 17 Rob Evans, 18 Dillon Lewis, 19 Cory Hill, 20 Ellis Jenkins, 21 Tomos Williams, 22 Dan Biggar, 23 Liam Williams.
Photo: Huw Evans Picture Agency