Youngest captains in Test cricket history

1)Mansur Ali Khan Pataudi (21 years 77 days) 

Captaincy debut: India vs West Indies at Bridgetown, Barbados on 23 March 1962 (lost by an innings and 30 runs)
Captaincy record: P40 W9 L19 D12

2)Javed Miandad (22 years 260 days)

Captaincy debut: Pakistan vs Australia at Karachi on 27 February 1980 (won by 7 wickets)

Captaincy record: P34 W14 L6 D14

3)Waqar Younis (22 years 15 days)

Captaincy debut: Pakistan vs Zimbabwe at Karachi on 1 December 1993 (won by 131 runs)
Captaincy record: P17 W10 L7 D0

4)Graeme Smith (22 years 82 days)

Captaincy debut: South Africa vs Bangladesh at Chittagong on 24 April 2003 (won by an innings and 40 runs)
Captaincy record: P109 W53 L29 D27

5)Tatenda Taibu (20 years 358 days)

Captaincy debut: Zimbabwe vs Sri Lanka at Harare on 6 May 2004 (lost by an innings and 240 runs)

Captaincy record: P10 W0 L9 D1

6)Mohammad Ashraful (22 years 353 days)

Captaincy debut: Bangladesh vs Sri Lanka at Colombo on 25 June 2007 (lost by an innings and 234 runs)

Captaincy record: P13 W0 L12 D1

7)Shakib Al Hasan (22 years 115 days)

Captaincy debut: Bangladesh vs West Indies at St George’s, Grenada on 17 June 2009 (won by 4 wickets)
Captaincy record: P9 W1 L8 D0