Angelo Mathews hit 97, accompanied by by Niroshan Dickwella’s 43, and Akila Dananjaya took six wickets as the hosts made 299 for eight off their 50 overs.
It left South Africa facing the biggest run chase ever required by a visiting team to the Colombo ground. They could not manage it and were all out for 121 in less than 25 overs.
Captain Quinton de Kock made a half century (54) but other wickets fell regularly as Dananjaya (six for 29) had the visitors in all sorts of trouble with his spin bowling.
Despite the heavy defeat, South Africa won the five-match series 3-2.
“Akila knows what he’s doing with the ball. It’s hard to take on someone like this when he has so many variations up his sleeve,” said South African skipper Quinton de Kock.
“We have batted well against him in this series, but today he bowled really well.”
Sri Lanka skipper Mathews said the team should have come up with such a performance earlier in the series.
“This was a performance we were looking for but it came in the last match. If we had been like that in the first three games things could have been a lot different,” said Mathews.
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