The win also sees England overtake India at the top of the ICC Men's T20 team rankings, with India slumping to their sixth defeat in their last seven matches.
Buttler came into this match after posting an underwhelming score of eight in England's nine-wicket win in Bristol, but alongside Harry Brook, he bludgeoned away the attacks of the Indian bowlers, hitting 12 fours and eight sixes to bring up his highest-ever score in the T20 international format of 131 runs from 64 deliveries.
"I'm delighted," Buttler said on his ton. "I've had a little bit of a lean patch, so I'm really happy to get back to my best and contribute to a brilliant series win."
After losing Phil Salt for just six runs off nine deliveries, Buttler and Brook brought up the highest second-wicket partnership in T20I history, smashing their way to 233 runs off 103 deliveries, before Buttler was removed after he clipped a delivery from Shivam Dube in the air to India captain Shreyas Iyer.
While Brook rode his luck at the start of the innings, surviving a dropped catch from Dube in the sixth over, he would go on to advance to a score of 95 off 45 deliveries.
"Harry [Brook] is just an incredible player," Buttler added. "It's great watching him put so much pressure on the bowlers. I just found my form, didn't fight it too much. It was great to spend a lot of time with him and build that innings.
"It's a great team performance. To beat India 4-0 is a fantastic achievement."
England set India a mammoth run chase of 258 to win, and despite half-centuries from Ishan Kishan and Tilak Varma, India's batters could not cut the deficit to England's giant lead.
Abhishek Sharma fell first for just three runs and was caught behind the stumps by the man of the moment, Buttler, off a Jofra Archer delivery.
Sam Curran was the pick of England's bowlers, taking a trio of wickets during the match. He removed Sanju Samson first, with the India opener chipping the ball up to Jacob Bethell on the off-side.
India appeared to regather some momentum, bringing up a score of 110 for a loss of four wickets, before Liam Dawson, who returned to the side for the final T20, removed Iyer, who edged the ball out to Curran at backward point.
Salt then produced an exceptional diving catch on the boundary to snare Kishan, who advanced to 56 off 35 balls, off an Adil Rashid delivery, leaving India struggling at 131 runs for a loss of four wickets.
Curran then had Dube for 14 runs, before Josh Tongue and Buttler combined to remove Varma, who had brought up a dangerous score of 53 from 25 balls.
From there, England pressed on, dismissing both Suryansh Shedge (7) and Axar Patel (3) in the 18th and 19th overs, with Arshdeep Singh (4) and Prasidh Krishna (1) running out of deliveries.
Brook: We deserve to celebrate
Reacting to his side's new status as the top-ranked T20 side in the world, Brook told Sky Sports he was delighted.
"We had a lot of fun," Brook said. "Jos and I bounced off each other, ran well, hit boundaries and complemented each other. We were just trying to get ourselves in the best position we could to defend a big total.
"Cricket is such a simple game, we make it so complicated. I just wanted to stand there, watch the ball, and play the shot the ball deserved.
"I'm striking the ball nicely, I'm in a good place with my game, but we've managed to get ourselves to world No 1. We're extremely happy, all the boys are delighted, and we deserve a bit of a celebration."
Watch all three games from England's ODI series against India LIVE on Sky Sports. Coverage of the first ODI commences on Tuesday July 14 on Sky Sports Cricket and Sky Sports Main Event from 10.30am, with the first ball at 11am. Stream cricket and more sport contract-free with NOW.
