Ostlund had already won Cannes' top honour for his film The Square in 2017. Triangle of Sadness, which features Woody Harrelson as a Marxist yacht captain and a climactic scene of rampant vomiting, pushes the satire even further.
"We wanted after the screening (for people) to go out together and have something to talk about," said Ostlund.
"All of us agree that the unique thing with cinema is that we're watching together. So we have to save something to talk about but we should also have fun and be entertained."
The jury's second prize, the grand prix, was shared between Lukas Dhont's tender boyhood drama Close and director Claire Denis' film Stars at Noon.
Korean star Song Kang Ho was named best actor for his performance in Japanese director Hirokazu Kore-eda's film Broker, about Korean family seeking a home for an abandoned baby.
"I'd like to thank all those who appreciate Korean cinema," said Song, who also starred in Bong Joon Ho's Palme d'Or winning film Parasite in Cannes three years ago.
Best actress went to Zar Amir Ebrahimi for her performance as a journalist in Ali Abbasi's Holy Spider, a true-crime thriller about a serial killer targeting sex workers in the Iranian religious city of Mashhad.
Violent and graphic, Holy Spider wasn't permitted to shoot in Iran and instead was made in Jordan. Accepting the award, Ebrahimi said the film depicts "everything that's impossible to show in Iran."
The awards were selected by a nine-member jury headed by French actor Vincent Lindon.
The jury prize was split between friendship tale The Eight Mountains, by Charlotte Vandermeersch and Felix Van Groeningen, and Polish director Jerzy Skolimowski's EO, about a donkey's journey across a pitiless modern Europe.
"I would like to thank my donkeys," said Skolimowski, who used six donkeys while making the film.
Swedish-Egyptian filmmaker Tarik Saleh took best screenplay at Cannes for Boy From Heaven, a thriller set in Cairo's Al-Azhar Mosque.
This year's award for best first film, the Camera d'Or, went to Riley Keough and Gina Gammell for War Pony, a drama about the Pine Ridge Reservation made in collaboration with Oglala Lakota and Sicangu Lakota citizens.
Saturday's closing ceremony brought to a close a Cannes that has attempted to fully resuscitate the annual France extravaganza which was cancelled in 2020 by the pandemic and saw modest crowds last year.
This year's festival also unspooled against the backdrop of the war in Ukraine, which sparked red-carpet protests and a dialogue about the purpose of cinema in wartime.
Last year, the French body horror thriller Titane took the top prize at Cannes, making director Julia Decournau only the second female filmmaker ever to win the Palme. In 2019, Bong Joon Ho's Parasite triumphed in Cannes before doing the same at the Academy Awards.
This year, the biggest Hollywood films at Cannes - Elvis, Top Gun: Maverick, Three Thousand Years of Longing - played outside Cannes' competition line-up of 21 films.
But their presence helped restore some of Cannes' glamour after the pandemic scaled down the festival for the last two years.
