The bowlers then put up a dominant display to bundle out the Proteas for 131 in 19.1 overs and register their first victory of the series.
Leg-spinner Yuzvendra Chahal (3/20) and death overs specialist Harshal Patel (4/25) shared seven wickets between them.
Earlier, Gaikwad (57 off 35) and Kishan (54 off 35) gave a perfect start as India looked on course to set a 200-plus total in their must-win match.
But the South African bowlers made a strong comeback, claiming quick wickets. Hardik Pandya then played an unbeaten 31-run knock to take India over the 175-run mark
Brief Score:
India 179 for 5 in 20 overs (Ruturaj Gaikwad 57, Ishan Kishan 54; Dwaine Pretorius 2/29)
South Africa 131 all out in 19.1 overs (Heinrich Klaasen 29, Reeza Hendricks 23; Harshal Patel (4/25), Yuzvendra Chahal 3/20)
