After winning the toss and electing to bat, Australia posted 264 from 49.3 overs courtesy of important half-centuries from Steve Smith (73 off 96) and Alex Carey (61 off 57).
But the total wasn't enough, with Kohli scoring 84 off 98 balls as India chased down the victory target with 11 deliveries to spare.
India will face either South Africa or New Zealand in Sunday's final.Â
At 4-198 in the 37th over, Australia were on track for a score in excess of 300.
But the loss of Smith and Glenn Maxwell (7) in quick succession sparked a collapse of 6-66 as Australia fell away badly.Â
Kohli became enemy No.1 on Australian shores this summer when he purposely bumped into rising star Sam Konstas during a heated moment in the Boxing Day Test.
The 36-year-old Indian superstar struggled for runs during that Test series, but he has rediscovered his touch during the Champions Trophy.
Kohli posted an unbeaten 100 in the group stage win over Pakistan, and he was the key figure in India's run chase against Australia on Tuesday.
Although he only registered five boundaries during his innings, Kohli's ability to peel off important runs and rotate the strike meant Australia's inexperienced attack never felt comfortable.
Virat Kohli steadied the India chase in a crucial stand with Shreyas Iyer 👌— ICC (@ICC) March 4, 2025Watch live now in India on @StarSportsIndia Head here for broadcast details in other territories �� https://t.co/S0poKnxpTX pic.twitter.com/4kbuMuoO80
"I wasn't feeling desperate. I was happy knocking ones around," Kohli told Prime.
"When as a batsmen you start taking pride in hitting those singles into the gaps, that's when you know you're playing good cricket.
"And then you know you're in for a big partnership and (are able to) settle the nerves down a little bit."
Kohli received a life on 51 when Maxwell dropped a tough one-handed diving catch near the non-striker's end.Â
It continued a rare off night in the field for Australia, with opener Rohit Sharma dropped on 13 by Cooper Connolly and again on 14 by a diving Marnus Labuschagne.
Connolly made amends for his drop by trapping Sharma LBW for 28, and Australia sniffed a chance for victory when India slipped to 4-178.
But Kohli, KL Rahul (42no off 34 balls) and Hardik Pandya (28 off 24) slammed the door shut, ending Australia's hopes of adding to the Champions Trophy titles they won in 2006 and 2009.
Earlier, Australia's gamble on Connolly as a replacement for injured opener Matt Short backfired, with the 21-year-old all at sea on the way to making a nine-ball duck.Â
Smith received a huge slice of luck on 23 when he edged the ball onto his pads and it rolled to hit his off-stump - only for the bails to stay on.
Then when Smith was on 36, Mohammed Shami dropped a tough one-handed return catch.Â
Smith made the most of the double reprieve, registering four fours and one six in his measured knock.
His exit in the 37th over prompted a big collapse as Australia's hopes of posting a score in excess of 300 faded.
Their final total would have been even lower if not for the efforts of Carey, who batted well with the tail before making the ill-fated decision to come back for a second run in the 47th over.
Paceman Mohammed Shami led the way for India with 3-48, while spinners Varun Chakaravarthy (2-49) and Ravindra Jadeja (2-40) provided good support.
"I thought we could have put a few more (runs) on. We lost a couple of wickets at crucial times," Smith said.
"If we got 280-plus, things could have been different."
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