Manu Tuilagi, who made a successful comeback from a shoulder injury with an impressive run-out in the win over Melbourne Rebels on Tuesday is the only one of the Tigers tourists to miss out.
Head coach Warren Gatland has made five changes to his line-up for the second Test at Etihad Stadium in Melbourne on Saturday.
Scrum-half Youngs is promoted from the bench to replace Mike Phillips and joins brother Tom who continues at hooker.
Welsh flanker Dan Lydiate replaces Tom Croft, who is on the bench.
Tommy Bowe takes over from Alex Cuthbert on the right wing following his return to full fitness.
The other two changes are forced by injury with Parling replacing Paul O’Connell, who suffered a fracture to his right arm in the first Test, and Makovina Vunipola takes over Alex Corbisiero, who strained a calf muscle in the same game.
Croft joins club colleague Dan Cole among the replacements where he will provide cover at second row and flanker.
Gatland said: “We said after the First Test that we had improvement in us and we are confident that is the case. Several players have put their hands up this week and have forced their way into the Test side while several players have returned to fitness.
“We want players to constantly push for selection, we then select who is on form and who is available. Based on that we have selected a squad that is capable of winning the Test and securing the series.”
Live coverage of Saturday’s second Test is available on Sky Sports.
British & Irish Lions (v Australia, Saturday June 29, Melbourne)
15 Leigh Halfpenny (Cardiff Blues/Wales)
14 Tommy Bowe (Ulster/Ireland)
13 Brian O’Driscoll (Leinster/Ireland)
12 Jonathan Davies (Scarlets/Wales)
11 George North (Scarlets/Wales)
10 Jonathan Sexton (Leinster/Ireland)
9 Ben Youngs (Leicester Tigers/England)
1 Makovina Vunipola (Saracens/England)
2 Tom Youngs (Leicester Tigers/England)
3 Adam Jones (Ospreys/Wales)
4 Alun Wyn Jones (Ospreys/Wales)
5 Geoff Parling (Leicester Tigers/England)
6 Dan Lydiate (Dragons/Wales)
7 Sam Warburton (Cardiff Blues/Wales) Captain
8 Jamie Heaslip (Leinster/Ireland)
16 Richard Hibbard (Ospreys/Wales)
17 Ryan Grant (Glasgow Warriors/Scotland)
18 Dan Cole (Leicester Tigers/England)
19 Tom Croft (Leicester Tigers/England)
20 Sean O’Brien (Leinster/Ireland)
21 Conor Murray (Munster/Ireland)
22 Owen Farrell (Saracens/England)
23. Alex Cuthbert (Cardiff Blues/Wales)
15 Kurtley Beale (Melbourne Rebels)
14 Israel Folau (NSW Waratahs)
13 Adam Ashley-Cooper (NSW Waratahs)
12 Christian Leali’ifano (Brumbies)
11 Joe Tomane (Brumbies)
10 James O’Connor (Melbourne Rebels)
9 Will Genia (Queensland Reds)
1 Benn Robinson (NSW Waratahs)
2 Stephen Moore (Brumbies)
3 Ben Alexander (Brumbies)
4 Kane Douglas (NSW Waratahs)
5 James Horwill (Queensland Reds, captain)
6 Ben Mowen (Brumbies)
7 Michael Hooper (NSW Waratahs)
8 Wycliff Palu (NSW Waratahs)
16 Saia Fainga’a (Queensland Reds)
17 James Slipper (Queensland Reds)
18 Sekope Kepu (NSW Waratahs)
19 Rob Simmons (Queensland Reds)
20 Liam Gill (Queensland Reds)
21 Nick Phipps (Melbourne Rebels)
22 Rob Horne (NSW Waratahs)
23 Jesse Mogg (Brumbies)