Jan Vertonghen scored the only goal of the game in Sao Paulo as Belgium secured top spot in Group H, despite playing much of the match with ten men.
Marc Wilmots made plenty of changes to his Belgium starting 11, knowing they only needed a point to finish top of Group H.
It was they who started the better, with the best chance of the first half falling to Dries Mertens after 25 minutes. The Napoli winger has been in good form in the World Cup so far, but blazed his shot over from 8 yards out.
South Korea needed a win to have any chance of qualifying, and they were handed a great opportunity on 44 minutes when Belgium were reduced to 10 men. Steven Defour was given a straight red card for a two footed challenge on Kim Shin-Wook.
Despite playing with 10 men, it was Belgium who took the lead after 77 minutes. Substitute striker Divock Origi had a good shot parried by South Korea goalkeeper Kim Seung-gyu. The ball then fell to Tottenham defender Jan Vertonghen, who was marginally onside from the original shot, to easily pass the ball into the net and give Belgium a 1-0 lead.
South Korea were starting to get desperate but struggled to break down an organised Belgium side who played the whole of the second half with just ten men.
Belgium held on for the 1-0 win that maintained their 100% record in Group H, to qualify top of their group. South Korea was knocked out whilst only collecting one point from their three matches.