The Indians first restricted Australia to 166 for five and then rattled up the required runs with 11 balls to spare in a flood-lit contest at the Brabourne Stadium.
The left-handed Gambhir (63 off 52 balls) was the star performer as he not only notched up his fourth Twenty20 half-century but also laid the foundation with a 82-run second wicket partnership with Robin Uthappa (35 off 26 balls).
The capacity crowd at the stadium, already in a festive mood on the eve of Dusshera, burst into celebration as captain Mahendra Singh Dhoni’s hit the winning runs by clobbering Brett Lee for a mighty six.
The skies lit up with dazzling fireworks providing the perfect finish to the absorbing contest which also saw useful contributions by Yuvraj Singh (31 in 25 balls) and Harbhajan Singh, who conceded only 17 runs in his four overs.
Ricky Ponting’s men did not help their own cause as they helped the Indians with front-foot no-balls giving the batsmen free hits. Also, overthrows and inaccurate bowling added to the Indian score.
Earlier, Ponting played a captain’s knock of 76 in 53 balls to help Australia reach 166 for five after electing to bat first. Opener Adam Gilchrist hit two consecutive fours in RP Singh’s first over, but lost his stump on the fifth delivery when the score was 12.
Andrew Symonds could not make much effect as he was run out by the Harbhajan-Yuvraj combination when the score was 110.
Brad Hodge was caught and bowled by Irfan Pathan when the score was 116. At this stage, Ponting was joined by Michael Clarke and they together put up 42-run partnership before the former was bowled by Pathan.
