A collaboration between the two pop stars was reported last month by US media outlets, but the official confirmation came on Monday when Sir Elton shared an image to his official Instagram.
Details of the project are limited, but the new track will be titled Hold Me Closer.
Britney's return to the pop scene comes as the Toxic singer continues her legal battle with her father Jamie Spears over his alleged misconduct during her 13-year conservatorship.
Last month a US judge denied a motion by Mr Spears that the pop star should return to court to face further questioning over the controversial legal arrangement, which ended in November last year.
Judge Brenda Penny previously ordered that Mr Spears himself be deposed and face questions about alleged surveillance of the singer at her home.
This year the singer announced the devastating loss of her “miracle baby early in the pregnancy” with partner Sam Asghari. The couple said that they would keep trying to “expand their beautiful family”.
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