Steve Smith will become the third youngest cricketer to lead Australia's test side.
Cricket Australia on Monday anointed the nation's 45th test captain following Michael Clarke's serious hamstring injury, with Smith to serve as caretaker skipper at age 25.
Clarke remains the side's captain, with Smith appointed vice-captain.
CA's board discussed the issue on Sunday night, electing to elevate Smith ahead of Brad Haddin in a surprise move.
Only Ian Craig (22) and Kim Hughes (25) captained Australia's test side at a younger age.
