Aiden Markram hit the fastest World Cup hundred as South Africa made 428-5 - the highest score in the tournament's history - in a statement 102-run victory over Sri Lanka in Delhi.
Markram made his ton off 49 balls, one quicker than Ireland's Kevin O'Brien against England in Bangalore in 2011.
He finally fell for 106 from 54, after Quinton de Kock had earlier hit 100 from 84 balls and Rassie van der Dussen a 110-ball 108.
David Miller, who struck 39 from 21, and Marco Jansen then took the score beyond the previous record of Australia's 417-6 against Afghanistan in 2015.
Sri Lanka, who are coached by former England coach Chris Silverwood, crumbled amid the carnage on the flattest of pitches.
They leaked 21 wides and had to bowl the final two overs with another fielder up inside the ring because of a slow over-rate.
Matheesha Pathirana conceded 26 runs from the 43rd over, with the seamer's 10 overs costing 95 for one wicket.
They fought admirably with the bat - Kusal Mendis' thrilling 76 from 42 balls with eight towering sixes even giving them hope of the most unlikely of victories early on.
Charith Asalanka smacked 79 from 65 and captain Dasun Shanaka held up South Africa's progress with a defiant 68 off 62, but Sri Lanka were eventually dismissed for 326 in 44.5 overs.
With 754, it is the most runs scored in a Men's World Cup match.
South Africa's next match is against Australia in Lucknow on Thursday, while Sri Lanka travel to Hyderabad to play Pakistan on Tuesday.
Proteas power to record total
South Africa's in-form batting line-up has led to many, not for the first time in these competitions, tipping them as dark horses for a first white-ball title.
At the first opportunity they showed their prowess in devastating fashion.
After captain Temba Bavuma fell lbw to left-armer Dilshan Madushanka in the second over, De Kock and Van der Dussen built relatively carefully - reaching 48-1 after 10 overs and 118-1 from 20.
Van der Dussen, who was dropped at backward point on 71, scored all around the wicket, including reverse sweeps to the spinners.
De Kock increased his intent after reaching his 50 from 61 balls, playing his trademark flowing strokes.
His 12th four, a fine flick through mid-wicket, took him to his first World Cup ton but he top-edged Pathirana a ball later.
That brought in Markram, whose innings began with glorious straight drives before becoming increasingly brutal as he struck 14 fours and three sixes.
It was also the first time in a Men's World Cup three batters have scored centuries in the same innings.
Miller kept the scoring rate high, while it was a high straight six from all-rounder Jansen in the penultimate over that set the new record.
There was also 32 from 20, including three sixes, by Heinrich Klaasen - one of five South Africa batters in the top 15 of the world rankings.
Their bowling and fielding must improve, left-armer Jansen conceded 92 runs for his two wickets and two catches were dropped, but the rest of the tournament should take note.
'Their total was a little too much' - reaction
Player of the match, South Africa batter Aiden Markram: "It obviously feels fantastic. The platform was laid beautifully by Quinton de Kock and Rassie van der Dussen, which allowed us to go out and play naturally.
"I am pretty clear with what is expected of me. Assess the situation and play accordingly. Sometimes it works well and sometimes it does not."
Sri Lanka captain Dasun Shanaka: "I expected a high-scoring game. The execution was not there, we were missing the right length. On these kind of wickets that's very tough.
"We had the momentum, especially the way that Mendis and Asalanka played, but their total was a little too much for us."
South Africa skipper Temba Bavuma:"Happy for us. I can't find fault with the batting. We were not quite clinical with the ball but we will take that confidence into the next game."
