RCA Records dropped a never-before-heard song called "Swimming in the Stars," which was originally part of Spears' 2016 album "Glory."
The song is available for download on streaming services and can be ordered at Urban Outfitters as part of a limited edition "Glory" vinyl record.
The album was actually re-released in May and featured another relatively new song called "Mood Ring," which was originally only featured as a bonus song on the album released in Japan.
It beat out Lady Gaga's “Chromatica," landing at the No.1 spot on iTunes.
Spears spent her birthday in Hawaii with her boyfriend Sam Asghari. "Felt like a little trip to paradise for an early birthday celebration," the singer wrote on social media as they stood next to a private jet.
The former Las Vegas performer and the fitness model, 26, have been dating since 2017. They first met on the set of her music video for “Slumber Party” in 2016.
Asghari penned a sweet message to the birthday girl on Instagram. "Happy Birthday to my Lioness 🥳 🎂 🎉 we’ve been celebration [sic] we will celebrate until the end of the year ❤️ let the cake eating began......" he wrote.
In November, Spears assured fans she's doing well despite some legal drama going on in her life.
"Hi. So I know that there have been a lot of comments and a lot of people saying a lot of different things about me, but I just want to let you guys know that I am fine," the pop star declared.
Spears added: "I'm the happiest I've ever been in my life."
The mother of two ended the video, "I'm sending all of you guys a lot of prayers, wishes and a lot of love.”
The star had a tumultuous year as she has fought to end a long conservatorship that puts her under legal guardianship under her father Jamie. He largely makes choices about her financial and personal life.
This past summer, it was reported that Spears is "strongly opposed" to her father resuming duties as her sole conservator, while it was later reported that she has requested that a trust company take over such duties.
In August, the legal guardianship was extended into 2021.
Fox News' Naledi Ushe contributed to this report.