With Germany favoured to progress to the last 16 after their 6-0 thrashing of Morocco in the other Group H match in Adelaide on Sunday, Tuesday's match at Allianz Stadium was massive for both sides.
In the clash between the last two of the 32 nations to play their tournament opener, Colombia scored twice in nine first-half minutes to secure the points.
South Korea had the first three shots of the game, but Colombia looked the more consistent and dangerous side after the first 20 minutes.
Colombia, who were without suspended head coach Nelson Abadia, had 17 attempts to five, though recording just two more shots on target.
A well-taken 30th minute penalty from 33-year-old Catalina Usme, Colombia's all-time leading goalscorer, gave them the lead after a shot struck the arm of Shim Seoyeon.
Then 18-year-old Linda Caicedo, who survived a cancer scare earlier in her teens, doubled the lead.
The highly rated youngster, who plays for Spanish giants Real Madrid, surged down the left and cut inside before her curling shot from just outside the area squirmed through the hands of goalkeeper Yoon Younggeui.
Caicedo constantly threatened the South Korean defence and was named player of the match.
"I am extremely happy but this had to do with the collective work of everyone," Caicedo said.
"I wanted to contribute as much as possible to the team and I'm happy for the goal and the victory."
South Korea's best chance came in the 10th of almost 12 minutes of stoppage time in the first half.
Lee Geummin had a free header from seven metres out, but Colombian goalkeeper Catalina Perez pulled off a fine save.
South Korea couldn't overcome the defensive pressure of their opponents and hardly created any opportunities in the second half.
Coach Colin Bell said his side gave Caicedo too much space and their decision making was too slow.
He also questioned why the penalty wasn't reviewed.
"It was a little bit harsh because the ball was really well struck, that speed that distance, I don't know where Seoyeon would have to put her arms," Bell said.
In the second half Colombia had almost all of the chances, but lacked accuracy.
South Korean Casey Phair became the youngest player in women's World Cup finals history when the 16-year-old came off the bench in the 78th minute.
"She deserved to get the chance to play, she's trained really well, as good as anybody else," Bell said.
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