Bong Joon Ho and Jin Won Han have won the best original screenplay Oscar for "Parasite", becoming the first South Korean film to win an Academy Award.

There have only been five other original screenplay winners for movies written in a foreign language -- the last was Pedro Almodovar's "Talk to Her" in 2002, reports variety.com.

"Parasite" revolves around one family who cons their way into the employ of another, much wealthier, family. The film's themes centre around wealth and entitlement, the disappearing middle class and moral relativism in the face of survival.

"Parasite" is nominated in six Academy Award categories including director, production design, international feature film, film editing and best picture.

It has been a favourite since it claimed the Palme d'Or at last year's Cannes film festival, and earned $165 million at the worldwide box office thus far.

In his acceptance speech on Sunday night, an emotional Bong said that "writing a script is always such a lonely process. We never write to represent our country. But this is very personal".

"I thank all the actors who are here with me today for bringing this film to life," he added.

The movie also won in the international feature film category, defeating other nominees from countries like France and Spain. It was earlier called best foreign language feature.

"Happy to be first recipient under the new name (of the category)," Bong said.

There was a round of applause for the cast and crew of the film too.