Garry Ringrose will partner Jared Payne in the centres as Ireland make four changes for Saturday's Test against Australia.
Ringrose is one of two injury-enforced changes made by Schmidt, with Paddy Jackson starting at fly-half in place of British and Irish Lions' Jonathan Sexton, who is sidelined with a hamstring injury.
The 21-year-old Ringrose is picked to start at inside centre alongside Jackson. He fills in for Robbie Henshaw, who misses the game after suffering a concussion in a brutal collision with Sam Cane in the first half against New Zealand on Saturday.
Ireland had drafted Ulster centre Stuart Olding into their squad in midweek but Schmidt has opted against pairing him alongside Payne, his team-mate at club level.
Schmidt insisted Ringrose's performance under pressure at inside centre last weekend against the All Blacks had won the young gun another chance to impress in the 12 shirt.
"Really it's a reflection of his performance last week," said Schmidt. "I thought Garry stepped in and did incredibly well against New Zealand.
"He slipped a couple of tackles, got one line break and almost got another couple, and he was among our top tacklers.
"So it's another opportunity to invest in Garry.
"He's been in camp with us for a year and a half at different times, and he's been a bit of a long-term investment, that we want to take this opportunity to develop a bit further."
There is one further change to the back-line as Keith Earls is picked to start on the left wing over Munster team-mate Simon Zebo, who drops to the bench after starting both Tests against New Zealand.
In the forwards, Ulster second row Iain Henderson comes into the side at the expense of Munster's Donnacha Ryan, who is beaten out for a place in the match-day 23 by Connacht lock Ultan Dillane.
Both full-back Rob Kearney and blindside flanker CJ Stander have overcome concussion issues to start.
Stander's recovery means standout Leinster flanker Josh van der Flier must once again be content with a place on the bench, despite two barnstorming displays as a substitute against the All Blacks.
Captain Rory Best will win his 100th Test cap for Ireland against the Wallabies as he follows in the footsteps of Brian O'Driscoll, Ronan O'Gara, Paul O'Connell and John Hayes.
Ireland: 15 Rob Kearney, 14 Andrew Trimble, 13 Jared Payne, 12 Garry Ringrose, 11 Keith Earls, 10 Paddy Jackson, 9 Conor Murray; 1 Jack McGrath, 2 Rory Best (c), 3 Tadhg Furlong, 4 Iain Henderson, 5 Devin Toner, 6 CJ Stander, 7 Sean O'Brien, 8 Jamie Heaslip.
Replacements: 16 Sean Cronin, 17 Cian Healy, 18 Finlay Bealham, 19 Ultan Dillane, 20 Josh van der Flier, 21 Kieran Marmion, 22 Joey Carbery, 23 Simon Zebo
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