Vinicius Junior, Neymar, Richarlison and Lucas Paqueta all found the net as the five-time champions exploited yawning gaps in their opponents' defence to run riot.
As the favourites eased down after the break South Korea showed plenty of intent in attack and grabbed a deserved consolation goal in the 76th minute when Seung-ho Paik let fly from the edge of the box.
A scintillating first-half performance that will live long in the memory was kicked off in the seventh minute by the brilliant Vinicius who threaded a delicious effort through a swarm of South Korean defenders to grab the opener.
Neymar, back after missing the previous two games with an ankle injury, swept home a cheeky penalty in the 12th minute after Richarlison was rather harshly adjudged to have been fouled in the box.
His goal took Neymar to within one of matching Pele's all-time record for their country and it was clear from their flamboyant celebrations that this Brazilian team boasts a team spirit to match the best of their predecessors.
Despite their ineptitude at the back, the South Koreans looked sharp when they went forward, and Hwang Hee-chan almost reduced the deficit when he hit a brilliant shot from 25 yards that Alisson Becker superbly tipped over the bar.
Richarlison rounded off a brilliant team move in the 29th minute when he placed Brazil's third past Kim Seung-gyu after an audacious, defence-splitting pass from centre-back Thiago Silva.
Brazil continued to surge forward and Paqueta made it four in the 36th minute with a superb side-foot volley after meeting Vinicius' delicate lob into the box.
Paqueta, Raphinha and Richarlison all spurned golden opportunities in four minutes of first-half injury time as the South Koreans threatened to be swept aside.
But to their credit Paulo Bento's side rallied after the break with Son Heung-min tearing into the box moments after the break where he was denied by Alisson with a good save.
The Liverpool stopper was forced into another fine save just past the hour mark after Hwang strode in from the right and hit a shot that was heading for the bottom corner.
Korea reduced the deficit as Brazil wound down but there was still time for Dani Alves to come close before the final whistle confirmed a weekend quarter-final against 2018 runners-up Croatia.