The singer-songwriter made the announcement on social media in celebration of her 31st birthday, teasing that 31 will be an important year in her life.
The Paramore frontwoman revealed on Twitter that she plans to release new music material in 2020, also hinting at possible collaborations with her "closest friends."
"Thanks so much for all the birthday wishes. 30 was a very important year. 31 will be too. I'm putting out some music next year. With the help of some of my closest friends, I made something I'm going to call my own," she tweeted, adding that fans will discover this "special project" as soon as next January.
Williams' solo project will arrive two years after Paramore released its fifth studio album, "After Laughter," which marked the return of original bandmate Zac Farro.
The group has been on an unofficial hiatus from music since 2018. Williams told online publication L'Odet that she still sees a long future for Paramore.
"We're all friends and we all make music in different parts, together. So I feel like, yes, I want to be in Paramore. I never want to have to put out a press release that says we're over or that I quit or that we're taking a hiatus, which is essentially a marketing ploy these days [...]. If we choose to move into it as a brand and put a name on these songs and make a new t-shirt, then awesome. But I've been in a band with them since I was 12; I don't think the band is going anywhere. As long as we're friends, the band just is. It's just in us," she explained.
In addition to Paramore, Williams has collaborated with several artists in recent years, including Chvrches and Tegan and Sara.
Last January, she teamed up with Illinois rock band American Football for "Uncomfortably Numb," which appeared on American Football's third eponymous studio album.
Next year, Williams will bring the Sanctuary of Self-Love camping ground back to Bonnaroo Music and Arts Festival from July 11 through 14 in Manchester, Tennessee.