Eighth Grade Photo: Courtesy of Sundance Film Festival
Burnham beat off competition from the heavily touted Roma and Green Book with his coming-of-age drama, while Holofcener and Whitty were also considered underdogs with their comedy drama about literary forger Lee Israel in a field that included BlackKklansman and If Beale Street Could Talk.
In her acceptance speech, Holofcener said: “I want to thank Lee. She’d probably be sitting in the room judging all of us. She though she was the smartest person in the room and she probably was.”
Burnham - who has not in the running for next week's Oscars - credited his young star Elsie Fisher for winning the award.
He said: “To the other nominees in the category — Have fun at the Oscars, losers!"
The Documentary Screenplay award went to Bathtubs Over Broadway, written by Ozzy Inguanzo and Dava Whisenant, about musicals produced by corporations for their staff.