Loose head prop Corbisiero has recovered from a calf injury to reclaim the number one shirt - the England man's importance to the Lions scrum evident ever since his 51st minute departure in the first Test.
Other changes see 2009's star tourist Jamie Roberts make his first Test start down under, the bruising centre edging Brian O'Driscoll out of the squad altogether, while another Welshman, Mike Phillips, is scrum-half of choice.
Up front Richard Hibbard, Sean O'Brien and Toby Faletau join Corbisiero with Alun Wyn Jones assuming the captaincy from the injured Sam Warburton.
"It all comes down to Saturday," head coach Gatland said. "Winner takes all. We know we can leave nothing in the tank and that only a complete performance will get us across the line. Picking this team was not easy and ultimately with several players available after recovering from injury the head overruled the heart in many selection decisions.
"It has been a challenging tour and we have had our fair share of injuries but we always knew that would be the case. Brian O'Driscoll is a great player and has had a wonderful career but for the final Test in Sydney we just felt Jamie Roberts' presence offered us something more.
"Mike Phillips and Alex Corbisiero were first Test selections and would probably have played in the second Test if not for injury. Richard Hibbard, Toby Faletau and Sean O'Brien have also earned their starting places."
BRITISH AND IRISH LIONS SIDE TO FACE AUSTRALIA
Third Test
Sydney
Saturday, July 6th, 2013
Kick off 11:05am BST
Live on Sky Sports 1 HD
15 Leigh HALFPENNY (Cardiff Blues and Wales)
14 Tommy BOWE (Ulster and Ireland)
13 Jonathan DAVIES (Scarlets and Wales)
12 Jamie ROBERTS (Racing Metro and Wales)
11 George NORTH (Northampton Saints and Wales)
10 Jonny SEXTON (Racing Metro and Ireland)
9 Mike PHILLIPS (Bayonne and Wales)
1 Alex CORBISIERO (Northampton Saints and England)
2 Richard HIBBARD (Ospreys and Wales)
3 Adam JONES (Ospreys and Wales)
4 Alun WYN JONES (Ospreys and Wales)
5 Geoff PARLING (Leicester Tigers and England)
6 Dan LYDIATE (Racing Metro and Wales)
7 Sean O'BRIEN (Leinster and Ireland)
8 Toby FALETAU (Dragons and Wales)
Replacements
16 Tom YOUNGS (Leicester Tigers and England)
17 Mako VUNIPOLA (Saracens and England)
18 Dan COLE (Leicester Tigers and England)
19 Richie GRAY (Castres and Scotland)
20 Justin TIPURIC (Ospreys and Wales)
21 Conor MURRAY (Munster and Ireland)
22 Owen FARRELL (Saracens and England)
23 Manu TUILAGI (Leicester Tigers and England)
