Andreas Schjelderup scored early and Benfica held on amid oppressive conditions for a 1-0 victory over Bayern Munich on Tuesday afternoon in Charlotte.
Anatoliy Trubin made four saves to keep Benfica's second consecutive clean sheet and preserve its first-ever competitive victory over Bayern as the Portuguese club finished atop Group C and extended their Fifa Club World Cup campaign.
Benfica (2-0-1, 7 points) will face either Chelsea or Esperance de Tunis, who play later on Tuesday to decide the second spot in Group D, in a Saturday round-of-16 clash also in Charlotte.
A heavily rotated Bayern (2-1-0, 6 points) had already clinched their spot in the knockout phase and will face Group D winner Flamengo on Sunday in Miami Gardens, Fla.
Benfica went in front 13 minutes into a sluggish first half that was played amid temperatures hovering around 97 degrees and beneath bright sunshine.
Ángel Di María played a ball wide down the right for Fredrik Aursnes, who then dragged a low cross back to the penalty area. That's where Schjelderup met it in stride and fired a low first-time finish past Manuel Neuer.
Trubin was exceptional after halftime as Benfica weathered increasing Bayern pressure.
In the 51st minute, Leroy Sané ran onto Joshua Kimmich's ball over the top but was denied by Trubin, who also made a more comfortable save of Thomas Müller's follow-up effort seconds later.
Kimmich thought he'd scored from the edge of the penalty area in the 61st minute, but the goal was ruled offside because Harry Kane was standing in an offside position and in the goalkeeper's view.
In the 74th minute, he denied Aleksandar Pavlovic with an outstretched leg from about 10 yards after Bayern's initial cross from the right rattled off a few bodies inside the area.
Then in the 87th, he thwarted Sané on the break for a second time after Sané ran onto Harry Kane's excellent through ball.