The Wallabies moved quickly to close a deal for McKenzie after releasing Robbie Deans late last night, six months before his contract was due to expire.
Australian Rugby Union chief executive Bill Pulver introduced 1991 World Cup winner McKenzie as head coach today, with the 48-year-old insisting that he is confident of making an instant impact in the role.
He told reporters: "To coach the Wallabies is a huge honour and also a special opportunity to lead a team that I've enjoyed many great experiences with in the past as both a player and coach.
"As a role at the highest level, it's one I aspire to because I truly believe I'm ready to make a difference on many levels.
"It's not a role without challenges but is also one that comes with great opportunity and a chance to influence the current state of rugby. I feel I can make a difference both on and off the field."
Australia are still reeling from their series defeat to the British and Irish Lions, which was sealed by a 16-41 loss in the third Test last weekend.
McKenzie will take charge of his first match as Wallabies coach in a clash with New Zealand on August 17.