Markram smashed a 49-ball century while the South Africans piled up 428 to defeat Sri Lanka by 102 runs in their opening fixture at the Arun Jaitley Stadium on Saturday.
The 29-year-old Markram, who went on to make 106, beat the previous record for the fastest World Cup century which was claimed by Ireland's Kevin O'Brien off 50 balls against England at Bengaluru in 2011.
South Africa surpassed the previous World Cup best total of 417 made by Australia against Afghanistan at Perth in 2015.
Top-10 all time total
Their 428-5 was also the ninth highest total in all one-day internationals.
"The way batters are playing nowadays, you wouldn't be surprised if that record is broken in this comp as well," said Markram who ended his innings with 14 fours and three sixes.
"There's a sort of see-ball-hit-ball sort of mentality. We're thankful that we got a belter of a wicket there tonight.”
Markram's first 50 on Saturday came from 34 balls while he needed only 15 more deliveries to add the next 50.
"It was nice for us to be able to go through the gears as a unit," added Markram after his third ODI century.
"I think a lot of credit has to go to Rassie and Quinny for setting up that platform. It's hard work always up front.”
He added: "It's quite strange because you almost get this thing that just takes over your body at certain moments.
"I think there's a lot of passion in this team to give our absolute all at this World Cup and see how far it can get us. We're known to start pretty slowly.”
Strong Sri Lankan start
Sri Lanka, to their credit, also had their foot on the accelerator for large parts of their reply.
Kusal Mendis (76), Charith Asalanka (79) and skipper Dasun Shanaka (68) all hit fine half-centuries in a total of 326.
At one point, Sri Lanka were looking strong at 109-2 in the 13th over.
"If we hadn't lost those few wickets in the middle overs, I believe we would have had a chance to come close to their score or even win the match," said Sri Lanka batsman Sadeera Samarawickrama.
Sri Lanka are next in action on Tuesday against Pakistan at Hyderabad while South Africa tackle five-time champions Australia in Lucknow on Thursday.