The first studio recording by Queen in 10 years will be available to download for free to promote World Aids Day.
May and Taylor are ambassadors for Mandela's 46664 campaign
Say It's Not True was written by Roger Taylor especially for Nelson Mandela's Aids awareness campaign, 46664.
"It's been a magical experience, fantastic," Taylor said of Queen's return to the studio on the BBC's Breakfast programme.
The track can be downloaded from the 46664 and Queen websites from Saturday, which is World Aids Day.
It is also available on Paul Rodgers' website - Rodgers took on the role of lead singer for Queen in 2004.
Taylor said the Aids cause was close to the band's heart.
"We are inextricably linked with that after losing Freddie," he told BBC Breakfast.
Rodgers was a founding member of the band Free
Queen, led by flamboyant frontman Freddie Mercury, released a string of hit records throughout the '70s, '80s and '90s - including Bohemian Rhapsody in 1975, widely regarded as one of the best UK singles of all time.
Mercury died from an Aids-related condition in 1991.
"By making the song available for free, we hope to help Nelson Mandela with his campaign to get across the message that no-one is safe from infection," said Taylor.
The 46664 charity is named after Mandela's prison number.
Queen's last studio recording was in November 1997 when May, Taylor and the band's bassist reunited to record No-One But You.
The song was written by Brian May and was heavily influenced by the loss of Mercury.