Regarded as one of the greatest rock singers of all time, Mercury was the lead singer of the 1970s rock group Queen. He died in 1991.
The honour was announced on Sunday in a YouTube video by Brian May, the former Queen guitarist who became an astrophysicist after the band broke up, the New York Times reported on Tuesday.
The rock, previously called asteroid 17473, shall henceforth be known as "Freddiemercury", the International Astronomical Union said.
"It's like a cinder in space, as many of these asteroids are," said May, who also has an asteroid already named after him.
"You need a pretty decent telescope to see it. It's just a dot of light but it's a very special dot of light, and maybe one day we'll get there," he noted.
Reading a citation from the Astronomical Union celebrating Mercury's musical achievements, May said, "His incredible vocal range and distinctive sound and performance style made him one of the most well-known icons of rock music."
"And he is regarded as one of the greatest rock singers of all time," the citation said.
Mercury, who was born Farrokh Bulsara, died in London in 1991 at age 45 from complications of AIDS.
The asteroid now bearing his name was discovered the same year, May said.
Discovered by the Belgian astronomer Henri Debehogne, the freshly-named asteroid, a 3.5km-wide ball of black rubble on the other side of Mars, swings around the sun at 20 km per second. Its slightly elliptical orbit never comes closer than 350 million kilometres to the Earth, meaning that the heavenly body called Freddiemercury poses no imminent danger to the planet, the Guardian reported.
