The LA-born soul singer joins artists like Adele, Jessie J and Ellie Goulding in topping the BBC’s annual poll, which tips the year’s musical success stories.
This latest win follows her triumph in the Brits Rising Star Award in December.
Celeste received 30 first-place votes from the 170 pundits who voted for the Sound of 2020.
Indie band Easy Life came second and pop-punk agitator Yungblud was named third in the poll.
Celeste was born in Los Angeles and raised in Brighton, where she started making music as a teenager.
The British-Jamaican singer wrote her first song at 17 and has subsequently supported acts including Janelle Monáe, Neneh Cherry and Michael Kiwanuka.
Celeste says: ‘I’m really, really happy. It’s like all of the work that went in throughout the [last] year wasn’t invisible. I can’t wait now to see what the rest of the year will look like. I’m so thrilled and so excited. I can’t wait.’
BBC Radio 1 DJ Annie Mac comments: ‘Her songwriting is personal and poignant but with universal appeal. I think she could easily join the long list of Sound Of winners who went on to be global stars.’