The pop star posted a 21-second black-and-white clip on Twitter, showing her putting a cassette bearing the song’s title, Easy On Me, into a car stereo.
That’s followed by 13 seconds of the song’s instrumental piano introduction.
Her tweet said Easy On Me will be released on Friday, 15 October, with her fourth album expected to follow.
It comes after posters and projections appeared around the world bearing the number 30, which is expected to be the title of the highly anticipated album.
The clip was watched six million times in the first hour on Twitter and Instagram.
Known for chart-toppings ballads such as “Hello” and “Someone Like You”, Adele posted the black and white video on her Twitter and Instagram pages on Tuesday, with the caption “Easy On Me – October 15”.
The video shows the singer in a car, putting a tape into a cassette player, checking the rear view mirror, increasing the volume and then driving off in a vehicle carrying packed up belongings. Soft piano music plays in the background as sheets of music fly out of the window.
Adele released “25” in November 2015. It topped charts around the world and scooped the coveted album of the year prize at the Grammy Awards.
Over the last few days, her fans have speculated online that the 33-year-old was set to release new music as the number “30” was mysteriously beamed onto buildings around the world.
Adele has referenced her age when naming her past three albums, “19”, “21” and “25”.