Steven Smith will captain the Australian cricket side for the rest of the series against India.
The 25-year-old replaces Michael Clarke, who suffered a serious hamstring injury during the first test win over India in Adelaide at the weekend.
Smith edged out veteran wicketkeeper Brad Haddin, who was the other contender to replace Clarke.
Haddin was named vice-captain.
Smith is Australia's youngest Test captain since Kim Hughes in 1979, and he's the third-youngest of all-time.
Ian Craig was just 22 when he took over the job in 1958.
Smith has prior experience as a skipper, leading New South Wales state in domestic competition and the Sydney Sixers in the local Twenty20 league.
He led Australia out for the second Test against India in Brisbane on Wednesday. The hosts lead the series 1-0.
Meanwhile Clarke's career now hangs in the balance, with the 33-year-old revealing fears he will never play again.
Cricket Australia A is continuing to consult with specialists over the best way to treat Clarke's latest tear.
Because of the uncertainty regarding the latest setback, selectors opted to put Smith in charge for the rest of the four-Test series.
"There was a strong argument for Brad to assume the captaincy until Michael returns," chief selector Rod Marsh said in a statement.
"But given we don't know how long that will be, we felt the time was right to take a longer-term view and give a young player this chance.
"Brad Haddin has done an exceptional job as vice-captain since assuming the role last year and will provide strong support to Steve just as he has done for Michael."
Smith has played 23 Tests, but only cemented his spot in the batting order during last year's back-to-back Ashes series.
The right-hander has impressed many with his temperament at the crease in his 18 Tests since earning a recall during Australia's woeful tour of India last year, scoring 1490 runs at an average of 51.37.
His leadership at New South Wales and the Sydney Sixers has also been widely praised.
"He is an exceptional young man who is highly regarded by the national selection panel, not only for his fine performances with the bat but also his maturity and clear leadership potential," Marsh said.
"These are difficult circumstances given Michael's injury and the fact that we don't know how long he will be out of the game.
"What we do know is that it won't be an overnight fix, so after a lot of thought we have taken the opportunity to appoint an emerging young leader as captain until such time as Michael regains fitness and returns."