India recover from 2-3 to win by six wickets
Kohli (85) & Rahul put on 165 for fourth wicket
Marsh drops Kohli on 12
Australia struggle on slow, turning pitch - slumping to 199 all out
Warner (41) & Smith (46) top-score but lack fluency
Jadeja (3-28), Kuldeep (2-42) & Bumrah (2-35) star with the ball
Marsh c Kohli b Bumrah 0 (Aus 5-1)
An early breakthrough!
Jasprit Bumrah finds the edge of Mitchell Marsh's bat and it's a huge dive from Virat Kohli at first slip, tumbling to his left to snaffle the Australia opener.
Are India setting the tone early on?
First boundary of the match for Warner! He slashes Mohammed Siraj's first delivery through backward point.
The Indian seamer follows up with five dot balls. Warner considers taking a sharp run to point but thinks again about taking on Ishan Khan's throw.
Carlos Brathwaite
West Indies all-rounder on BBC Test Match Special
I think Mitch Marsh is very important to this Australia side in his role as opener given how dynamic he is with bat in hand.
Bumrah hustles in with his distinctive upright action and whistles his opening ball past Warner's bat.
The opener takes a run for the following delivery, pushing one to point, before Mitchell Marsh plays out the rest of the over.
Australia opener Mitchell Marsh is leaning on his bat at the non-striker's end, while partner David Warner does some final stretches at the other end of the wicket.
Jasprit Bumrah is lurking at the end of his run-up.
We're almost ready to go.
The teams are out to heartily sing their anthems. If you don't fancy a sing along, why not enjoy highlights from yesterday's South Africa-Sri Lanka match, where the two sides put on quite a show.
These teams met in a three-match series in the build-up to this tournament, with India taking victories at Mohali and Indore before Australia winning a consolation in Rajkot.
Prior to that, India were triumphant in September's Asia Cup, dismissing Sri Lanka for just fifty in the final.
Meanwhile Australia conceded a 2-0 lead in their series against South Africa, losing three matches in a row to go down 3-2.
India: Rohit Sharma (c), Ishan Kishan, Virat Kohli, Shreyas Iyer, KL Rahul (wk), Hardik Pandya, Ravindra Jadeja, Ravichandran Ashwin, Kuldeep Yadav, Jasprit Bumrah, Mohammed Siraj
Australia: David Warner, Mitchell Marsh, Steven Smith, Marnus Labuschagne, Glenn Maxwell, Alex Carey (wk), Cameron Green, Pat Cummins (c), Mitchell Starc, Adam Zampa, Josh Hazlewood
The big news out of the India camp is that opener Shubman Gill is not fit for selection. The batter had been good form in the warm-up series against Australia, hitting scores of 74 and 104, but has been diagnosed with dengue fever.
Less seriously, Australia select Adam Zampa despite him ploughing into the side of a swimming pool at the team's hotel.
India captain Rohit Sharma: "Conditions for the bowlers will be on the slower side, the ball will turn as the match goes on.
"We have played a lot of cricket recently so we are ready. We have covered all our bases and we're looking forward to this game."
Australia captain Pat Cummins: "It looks a good wicket. The sun is out, so it looks a good afternoon to bat.
"We are in a really good spot. We have played quite a lot over the last month but the we have got the right balance between game time and the lads feeling pretty fresh."
Australia captain Pat Cummins has won the toss and taken the decision to bat first at the MA Chidambaram Stadium stadium.
Image source, Getty ImagesA billion people have been waiting for four days. Or has it been four years?
The hosts are finally under way at this World Cup and who better to face than the five-time world champions?
It's India v Australia in Chennai - it doesn't get much bigger than this.