The husband-wife songwriting team, Kristen Anderson-Lopez and Robert Lopez, were awarded the golden statuette at the Dolby Theatre in Los Angeles.
Meanwhile, the award for the best original score was won by Alexandre Desplat for 'The Shape of Water'. In his winning speech, Desplat said, "Thank you for letting the music be the voice of your characters and convey the beautiful melancholy of love".
This is Desplat's second win at the Oscars; he had earlier won for 'The Grand Budapest Hotel' in 2015.
Desplat has received nine nominations till date over the course of his career.