Pic Courtesy: twitter.com/ICC
The 93-run win is India's biggest win in T20 Internationals, bettering the 90-run victory over England recorded in Colombo in September, 2012.
Sent into bat, Rahul's classy fifty and some sensible batting from Mahendra Singh Dhoni (39 not out) and Manish Pandey (32 not out) powered India to a challenging 180 for three.
Chahal then finished with brilliant figures of 4 for 23, taking wicket in each of his four overs to lead Sri Lanka's downfall as the visitors Lanka were bundled out for 89 in 16 overs on a dew-laden Barabati Stadium.
After the leg-spinner's guile, it was Kuldeep Yadav's turn to get into the act with figures of 2 for 18 as the wrist spin duo once again did the job for India.
It was yet another pathetic batting show by the Sri Lankans, who showed little resistance as wickets kept tumbling after Upul Tharanga's 16-ball 23-run burst.
Earlier, in the absence of first-choice opener Shikhar Dhawan, Rahul grabbed the opportunity with both hands hitting seven fours and one six en route to a 48-balls 61 after being put into bat by Sri Lanka skipper Thisara Perera.
Rahul and number three Shreyas Iyer (24) put together 63 runs from 46 balls as India looked to push for a 200-run mark on a two-paced Barabati wicket before Sri Lanka bounced back dismissing the duo in a span of 11 balls.
But former skipper Mahendra Singh Dhoni, who was promoted to number four, smashed an unbeaten 22-ball 39 and Pandey had other plans as the duo stitched an unbeaten 68-run stand off 34 balls for the fourth wicket to prop up India's total.
In reply, Sri Lanka showed hardly any fight.
Playing his first match since his T20I debut in June 2016, left-arm pacer Jaydev Unadkat (1/7) returned to the side with elan, giving India the breakthrough in the second over.
Unadkat dismissed Niroshan Dickwella (13) for his maiden T20I wicket as he conceded just seven runs in the first two overs before Chahal reigned supreme.
Chahal was hit for successive fours and six by a dangerous-looking Tharanga but he bounced back with Dhoni taking a superb catch down the leg side.
Chahal returned in the eight over and this time dismissed former Sri Lankan skipper Angelo Mathews, caught and bowled.
Chahal took his third after Asela Gunratne (4) was stumped by Dhoni before finishing his quota with the wicket of Sri Lankan skipper Thisara Perera.
Earlier, Rahul paced his innings brilliantly and also successfully reviewed to overturn an LBW decision when he was on 23.
Sri Lanka looked to attack through Mathews and brought him back in the ninth over to break the partnership.
Stepping out against Mathews, Rahul was hit awkwardly in the abdominal region when on 37 as he had to be attended to by the physio.
But he braved the pain and took on the Lankan former skipper and in the next ball dispatched Mathews over square leg with a crunching pull and completed his second T20 half-century in 34 balls.
There was no looking back for India but Sri Lanka slowed down the run-rate, removing Iyer and Rahul in space of 11 balls.
Iyer edged one behind the stumps and Rahul was deceived by a slower one by skipper Perera.
Dhoni came in at four to a rousing reception by a capacity crowd of 43,000 and he did not disappoint as India added 66 runs in the last five overs without losing a wicket.
Four off eight balls, Rahul decided to break free with an inside out lofted shot against Chameera en route to his boundary in the third over.
11 runs came from Danajaya's next over with boundary each by Rahul and Sharma as India were going strong for 38 for no loss from 29 balls when Mathews gave the first breakthrough dismissing the Indian skipper.
Looking to clear the midwicket, Sharma mistimed and a brilliant forward diving catch by Chameera ended his innings for 17, but not before he became the second Indian to reach 1500 T20 runs after Virat Kohli.
Sharma got to the milestone when he was on 15.
Sent into bat, Rahul's classy fifty and some sensible batting from Mahendra Singh Dhoni (39 not out) and Manish Pandey (32 not out) powered India to a challenging 180 for three.
Chahal then finished with brilliant figures of 4 for 23, taking wicket in each of his four overs to lead Sri Lanka's downfall as the visitors Lanka were bundled out for 89 in 16 overs on a dew-laden Barabati Stadium.
After the leg-spinner's guile, it was Kuldeep Yadav's turn to get into the act with figures of 2 for 18 as the wrist spin duo once again did the job for India.
It was yet another pathetic batting show by the Sri Lankans, who showed little resistance as wickets kept tumbling after Upul Tharanga's 16-ball 23-run burst.
Earlier, in the absence of first-choice opener Shikhar Dhawan, Rahul grabbed the opportunity with both hands hitting seven fours and one six en route to a 48-balls 61 after being put into bat by Sri Lanka skipper Thisara Perera.
Rahul and number three Shreyas Iyer (24) put together 63 runs from 46 balls as India looked to push for a 200-run mark on a two-paced Barabati wicket before Sri Lanka bounced back dismissing the duo in a span of 11 balls.
But former skipper Mahendra Singh Dhoni, who was promoted to number four, smashed an unbeaten 22-ball 39 and Pandey had other plans as the duo stitched an unbeaten 68-run stand off 34 balls for the fourth wicket to prop up India's total.
In reply, Sri Lanka showed hardly any fight.
Playing his first match since his T20I debut in June 2016, left-arm pacer Jaydev Unadkat (1/7) returned to the side with elan, giving India the breakthrough in the second over.
Unadkat dismissed Niroshan Dickwella (13) for his maiden T20I wicket as he conceded just seven runs in the first two overs before Chahal reigned supreme.
Chahal was hit for successive fours and six by a dangerous-looking Tharanga but he bounced back with Dhoni taking a superb catch down the leg side.
Chahal returned in the eight over and this time dismissed former Sri Lankan skipper Angelo Mathews, caught and bowled.
Chahal took his third after Asela Gunratne (4) was stumped by Dhoni before finishing his quota with the wicket of Sri Lankan skipper Thisara Perera.
Earlier, Rahul paced his innings brilliantly and also successfully reviewed to overturn an LBW decision when he was on 23.
Sri Lanka looked to attack through Mathews and brought him back in the ninth over to break the partnership.
Stepping out against Mathews, Rahul was hit awkwardly in the abdominal region when on 37 as he had to be attended to by the physio.
But he braved the pain and took on the Lankan former skipper and in the next ball dispatched Mathews over square leg with a crunching pull and completed his second T20 half-century in 34 balls.
There was no looking back for India but Sri Lanka slowed down the run-rate, removing Iyer and Rahul in space of 11 balls.
Iyer edged one behind the stumps and Rahul was deceived by a slower one by skipper Perera.
Dhoni came in at four to a rousing reception by a capacity crowd of 43,000 and he did not disappoint as India added 66 runs in the last five overs without losing a wicket.
Four off eight balls, Rahul decided to break free with an inside out lofted shot against Chameera en route to his boundary in the third over.
11 runs came from Danajaya's next over with boundary each by Rahul and Sharma as India were going strong for 38 for no loss from 29 balls when Mathews gave the first breakthrough dismissing the Indian skipper.
Looking to clear the midwicket, Sharma mistimed and a brilliant forward diving catch by Chameera ended his innings for 17, but not before he became the second Indian to reach 1500 T20 runs after Virat Kohli.
Sharma got to the milestone when he was on 15.
