Ronnie Dio's original band Elf was quite close with Deep Purple, being a regular opening act and having all their albums produced by Purple bassist Roger Glover.

A character representing Ronnie James Dio appeared in the third season episode of South Park titled "Hooked On Monkey Phonics", playing "Holy Diver" at the school dance. However, Ronnie James Dio himself did not provide the character's speaking voice.

Additionally, Dio was originally slated to voice the character Doviculus, in the heavy metal-influenced video game Brütal Legend, but was replaced by Tim Curry.

Also, Dio Brando, the primary antagonist of the manga series Jojo's Bizarre Adventure, is named after Ronnie James Dio.

One of the other musical projects of Ronnie James Dio include the collective fundraiser Hear 'n Aid. Hear 'n Aid was a joint effort from the heavy metal scene of the 80s to raise money for famine relief in Africa. Within a year, the project had raised $1 million. The album, exclusively built on artists from the heavy metal scene, was entitled "Stars" and the single was called "We're Stars". Ronnie James Dio had intended for the song and album to be released shortly after its recording, but contractual issues with the different artists' record labels delayed the release until January 1, 1986, somewhat diminishing the impact of its release.

"Dio" is the Italian word for "God". Ronnie took up the name "Dio" after mafia member Johnny Dio, and first used it professionally in the early 1960s, playing in a band called Ronnie Dio and the Prophets.

Ronnie James Dio is known for popularizing the sign of the horns in heavy metal. He claimed his Italian grandmother used it to ward off the evil eye (which is known in the Italian culture as "malocchio"). Dio began using the sign soon after joining the metal band Black Sabbath in 1979. The previous singer in the band, Ozzy Osbourne, was rather well known for using the "peace" sign at concerts. Dio, in an attempt to connect with the fans, wanted to similarly use a hand gesture. However, not wanting to copy Osbourne, he chose to use the sign his grandmother always made. The horns became famous in metal concerts very soon after Black Sabbath's first tour with Dio. The sign would later be appropriated by heavy metal fans under the name "maloik", a corruption of the original "malocchio".

The song "Rainbow In The Dark", from the album Holy Diver was, in Dio's opinion, one of the worst he wrote. He didn't want it to be included in the album, so he tried to destroy the tape with a razor, but the rest of the band stopped him in time!