Loosehead prop Rhys Carré comes into the front row alongside hooker Ryan Elias and tighthead prop Tomas Francis, with Wyn Jones moving to the replacements bench.
Dragons lock Will Rowlands links up with Ospreys lock Adam Beard in the second row to win his 12th international cap.
Cardiff Rugby’s Ellis Jenkins comes in for Moriarty in the back row, making his long-awaited return to international rugby after suffering a knee injury against South Africa three years ago. Dragons pair Taine Basham and Aaron Wainwright retain their places in the loose trio.
Tomos Williams remains at scrumhalf while the experienced Biggar, making his 93rd international appearance, returns to the starting line-up after touring with the British & Irish Lions.
Saracens centre Nick Tompkins partners up in midfield with Davies, with Louis Rees-Zammit linking up in the back three with fellow winger Josh Adams and fullback Johnny McNicholl.
The replacements include two debutants - hooker Bradley Roberts, who was born in South Africa, and tighthead prop WillGriff John - while fullback Liam Williams has made a return to fitness, after undergoing an appendectomy, and will take part in his first game of rugby since the last British & Irish Lions Test, against South Africa, back in August.
“South Africa coming to town, as World Champions, offers a different challenge to New Zealand," said Pivac.
"They’ve got a massive forward pack, they’re big across the park really, and they bring a huge aerial threat so it’s going to be a different challenge.
“It’s a big test match and we need to get what we think is the best side out there. We’re looking forward to having this side out there on the weekend and it’ll be really interesting to see how we go.
“There’s a lot of experience gone from the pack now and with what’s coming in terms of the South African pack, with their experience, it’s going to be a massive challenge for our boys and it’ll be interesting to see who steps up.
“Field position in this game is going to be massive, with the scrum that’s coming and line out drive, so we have to make sure we’re smart in how we play the game.
Wales team to face South Africa:
15 Johnny McNicholl (Scarlets)
14 Louis Rees-Zammit (Gloucester Rugby)
13 Jonathan Davies (captain, Scarlets)
12 Nick Tompkins (Saracens)
11 Josh Adams (Cardiff Rugby)
10 Dan Biggar (Northampton Saints)
9 Tomos Williams (Cardiff Rugby)
8 Aaron Wainwright (Dragons)
7 Taine Basham (Dragons)
6 Ellis Jenkins (Cardiff Rugby)
5 Adam Beard (Ospreys)
4 Will Rowlands (Dragons)
3 Tomas Francis (Ospreys)
2 Ryan Elias (Scarlets)
1 Rhys Carré (Cardiff Rugby)
16 Bradley Roberts (Ulster – uncapped)
17 Wyn Jones (Scarlets)
18 WillGriff John (Scarlets – uncapped)
19 Ben Carter (Dragons)
20 Seb Davies (Cardiff Rugby)
21 Gareth Davies (Scarlets)
22 Gareth Anscombe (Ospreys)
23 Liam Williams (Scarlets)