South Africa's World Cup hopes are hanging by a thread after Rohit Sharma's unbeaten 122 propelled India to a six-wicket victory at the Hampshire Bowl.
The Proteas succumbed to a third consecutive defeat after struggling to 227-9, a total India overhauled in 47.3 overs to open their campaign with an assured victory.
Sharma took centre stage after captain Virat Kohli (18) fell to a stunning one-handed catch by wicketkeeper Quinton de Kock, reaching his second World Cup hundred off 128 balls with a single off spinner Tabraiz Shamsi.
The century - the 23rd of Rohit's ODI career - takes him up to ninth spot in the list of most ODI hundreds, one spot ahead of compatriot Sourav Ganguly.
India's victory was founded on an impressive all-round bowling display in which seamer Jasprit Bumrah (2-44) and spinner Yuzvendra Chahal (4-51) stood out.
South Africa were quickly in trouble after choosing to bat and by the 23rd over had slipped to 89-5 off the back of a collapse in which three wickets fell for 11 runs.
Bumrah set the tone by finding the edge of Hashim Amla's bat before fellow opener De Kock snicked to Kohli in the slips - the score at that point 24-2.
Rassie van der Dussen (22) steadied the innings, sharing a 54-run stand with skipper Faf du Plessis (38), only to lose his middle stump attempting to reverse sweep Chahal - who went on to become the first Indian leg-spinner to take four wickets in a World Cup match since 2003.
Du Plessis fell in the same over and the procession continued with Kuldeep Yadav trapping JP Duminy lbw before Chahal induced a return catch from David Miller.
Andile Phehlukwayo (34) swelled his side's total before being stumped by a distance despite MS Dhoni's initial fumble and, but for a cameo of 42 from Chris Morris and Kagiso Rabada's 31 not out, a total of over 200 would have been well out of South Africa's reach.
With injured Lungi Ngidi on the sidelines and fellow seamer Dale Steyn ruled out of the tournament, Kagiso Rabada spearheaded South Africa's attack and did so impressively from the off.
The 24-year-old prised out Shikhar Dhawan for just eight in a fiery opening spell and, with spinner Imran Tahir and Morris also keeping things tight, India found runs hard to come by initially.
Kohli (18) looked happy to bide his time only to be undone by some extra bounce from Phehlukwayo - the resulting edge taken one-handed in spectacular fashion by De Kock high up to his right.
Sharma remained unhurried, breaking out from a range of cuts to strike an immense six over mid-wicket off Shamsi on his way to a 70-ball half-century.
KL Rahul (26) played the supporting role in a third-wicket stand of 85 before miscuing Rabada to mid-off but there was precious little respite for the Proteas as MS Dhoni (34) found the gaps adeptly.
With 57 runs needed off the final 10 overs of the innings, India were on cruise control and Miller gave them a helping hand by shelling a dolly at extra cover when Sharma spliced an attempted pull off Rabada when he had 107 to his name.
The right-hander made his life count straight away, leaning back to glide the very next ball over De Kock for four before he and Dhoni improved their stand to 74.
Dhoni fell with the victory in sight, miscuing a pull high into the air back to seamer Morris who took the catch coolly before tripping backwards over middle-stump and demolishing the stumps at the non-striker's end.
The incident brought smiles to South Africa faces - not least that of Morris himself - but South Africa's future in the tournament now looks bleak.
While the Proteas are not yet out, they do need to win at least five of their remaining games - and emphatically so - if not all six to stand a chance of reaching the semi-finals.
Watch Australia take on West Indies in the 2019 ICC Cricket World Cup, live from 10am on Sky Sports Cricket World Cup on Thursday.