Angelo Mathews hit 97 and Akila Dananjaya took six wickets as Sri Lanka hammered South Africa by 178 runs in the final one-day international in Colombo on Sunday.
With the brilliant innings from Mathews, backed by Niroshan Dickwella's 43, Sri Lanka made 299-8 off their 50 overs.
South Africa, needing to make the biggest target ever achieved by a visiting team to the Colombo ground, were all out for 121 after just under 25 overs.
Captain Quinton de Kock made 54 but other wickets fell thick and fast as Dananjaya's (6-29) spin took a toll on the visitors.
Despite their heavy defeat, South Africa won the five-match series 3-2.