The South Korean film, about a poor South Korean family infiltrating a wealthy household, beat heavy competition from films including the heavily favoured war epic 1917 to take home its fourth statuette of the night.
Earlier, it won the prizes for best director for Bong Joon-ho, best international feature and best original screenplay to become the big winner on Hollywood's biggest night.
"We never write to represent our countries," said Bong. "But this is (the) very first Oscar to South Korea. Thank you." — AFP