"Infinity" is a song by Japanese voice actress and recording artist Megumi Hayashibara. Written by Hidetoshi Sato with lyrics penned by Hayashibara, the song was released as a single on April 24, 1998, via Starchild.
The title track served as the opening theme for the TV Tokyo anime series Lost Universe created by Hajime Kanzaka, which happens in a world parallel to the one of Slayers. The anime, in which Hayashibara also voiced the character Canal Volphied, aired from April through September 1998 in Japan.
For the single release, the song was coupled with "Extrication", which served as ending theme for the same anime series. Both songs first appeared in full on the soundtrack album Lost Universe Tracks Contents 1 released on July 3, 1998, with subsequent Lost Universe albums including several alternative versions of the track. It was not included on any studio album by Hayashibara, but it was later included on her best-of album Vintage S, released on April 26, 2000.
The single was made available for streaming on March 30, 2021, along with the entire Megumi Hayashibara discography. The alternative versions of both "Infinity" and "Extrication" were made available for streaming by King Records on July 8, 2025, along with the entire Lost Universe discography.
"Infinity" debuted and peaked at number 8 on the Oricon charts, selling 64,040 copies on its first week. The single charted for nine weeks and sold a total of 141,510 copies, making it Hayashibara's fourth highest-selling single. Among her non-Slayers-related tie-in singles, it holds the top sales position.
Voice actor Sà Âichirà  Hoshi covered the song under the title "Re:Infinity" on his 2007 single "Starting Again".