The 18-year-old pop superstar took to Instagram to share a 20-second clip of the hotly-anticipated track, her first since her Bond song, 'No Time To Die’, and her acclaimed record-breaking debut LP, 'When We All Fall Asleep, Where Do We Go?'.
She simply captioned the post: "tomorrow", along with three see-no-evil monkey emojis.
The full single will follow at midnight BST/4pm PT (30.07.20).
On the track, Billie sings in her signature whisper-pop style: "Can’t you hear me? I’m not coming home / Do you understand? / I’ve changed my plans."
Earlier this year, the 'everything i wanted' hitmaker's sibling, Finneas O'Connell - who works as her producer - confirmed they were hard at work on her second album.
He said in March: "We've started working on the new album, and I think the best thing we can do is stay out of our own way. The first album was pretty pure in its intention. We didn't set out to write a darling album. Our only target was to make an album that we liked, to play live. I think that's all we're gonna do for the second. All the other things are side effects. You can't aim for those."
Last year, Finneas revealed Billie would be heading in an "experimental" direction following the success of the 2019 record, which saw her bag multiple awards, including becoming the youngest artist to sweep the main four categories at the Grammys.
He explained: "I think so far, in album two ... there's just a lot of stories we felt we didn't get to tell yet.
"We're just trying to tell all those and we're being a little bit experimental. I think if you're not trying to change things a little bit, you're not evolving. So I think we're just trying to embrace everything that we are proud of in our music and also just try new things and experiment and give people stuff to look forward to."