Shivnarine Chanderpaul guided West Indies into the ICC Champions Trophy semi-finals by hitting an unbeaten 51 in a tight five-wicket win over South Africa in their Group B decider at The Oval on Sunday.
Ricardo Powell also struck a crucial 16 from 10 balls as West Indies passed their target of 247 with just seven balls to spare in the closest finish of the tournament so far.
West Indies will face India or Pakistan in Wednesday's semi-final at the Rose Bowl, Southampton.
Ramnaresh Sarwan top scored with 75 before he was bowled by South Africa's Makhaya Ntini with five overs left to leave the game wide open.
Captain Brian Lara had earlier contributed 49 but West Indies struggled to keep the run rate up before Chanderpaul kept his cool late on to steer his side to victory.
West Indies resumed on 20 without loss after play was rolled over from Saturday when rain brought an early end to the day after Herschelle Gibbs's century had taken South Africa to 246 for six.
Gibbs had a torrid time with the bat in last month's tour of Sri Lanka and was in danger of the axe but he hit back with 101 from 135 balls on Saturday, including a six off spinner Chris Gayle to bring up his hundred.
Captain Graeme Smith also struck 45 in a 102-run opening stand with Gibbs while Gayle ended up with three for 50.