Youngs is one of two changes made by team manager Martin Johnson. He replaces Danny Care at scrum-half while Northampton Saints lock Courtney Lawes takes over from Simon Shaw for his first start.
Youngs said: "The excitement's boiling up already and if I can use that in the right way it'll help me put in a good performance on Saturday.
"I've played against [Australia's scrum half] Will Genia before at Under 20 level. He's a world class player and I'm really looking forward to the challenge and seeing where I stand against him."
Lewis Moody again captains the side from seven and is joined in the back row by Tigers teammate Tom Croft and Nick Easter.
Toby Flood partners Youngs at half-back, Dan Cole is at tighthead and George Chuter is named among the replacements.
England (vs Australia, second Test, Sydney, Saturday, June 19, 11am)
15 Ben Foden (Northampton Saints)
14 Mark Cueto (Sale Sharks)
13 Mike Tindall (Gloucester Rugby)
12 Shontayne Hape (Bath Rugby)
11 Chris Ashton (Northampton Saints)
10 Toby Flood (Leicester Tigers)
9 Ben Youngs (Leicester Tigers)
1 Tim Payne (London Wasps)
2 Steve Thompson (CA Brive)
3 Dan Cole (Leicester Tigers)
4 Courtney Lawes (Northampton Saints)
5 Tom Palmer (Stade Francais)
6 Tom Croft (Leicester Tigers)
7 Lewis Moody (Leicester Tigers) CAPTAIN
8 Nick Easter (Harlequins)
16 George Chuter (Leicester Tigers)
17 David Wilson (Bath Rugby)
18 Simon Shaw (London Wasps)
19 James Haskell (Stade Francais)
20 Danny Care (Harlequins)
21 Jonny Wilkinson (RC Toulon)
22 Delon Armitage (London Irish)