Opening theme songsBoth of the opening songs are epic rock pieces which really set the mood for the action in each episode.
- To start off, we've got THE HERO!!! ~Set Fire to the Furious Fist~ by JAM Project, which plays during every episode in Season 1.
- The live version is just as awesome.
- Then there's Jonathan Young's English version of the song, which manages to give the translated lyrics a better flow.
- There's also this English cover of the TV version of the song by NateWantsToBattle, which translates the Japanese lyrics very well.
- For added funny: some ballsy fans over at Reddit's Anime community did their rendition of the full song. And nailed it, and then some.
- Or this Spanish remake of the opening collab by some Latin American singers.
- Seijaku no Apostle by JAM Project, the next opening song for Season 2, brings up the heroic hype against the monsters. Jonathan Young also made another English version for this particular song.
Ending theme songsThe ending songs are also great, though they clash with the other tracks in how calm and peaceful they are.
- "I'll Find You Sooner Than the Stars" from Season 1 is a romantic piece, with the female singer (Hiroko Moriguchi) being concerned for Saitama. She has a rather hauntingly beautiful voice to go with the song's melancholic melody. Also check out this English version by Enn.
- "Embrace the Sadness", also sung by Hiroko Moriguchi, from the Season 1 finale (Episode 12) concludes the season's arc with this sweet tune.
- "No Map but I'll Be Back" from Season 2 seems to be a response to "I'll Find You Sooner Than the Stars", and gets extra points for being sung by Makoto Furukawa (Saitama's Japanese voice actor).
- The One-Punch Folk Songs are a series of short, comical ending themes sung in-character by the Japanese voice cast during the credits of the OVA episodes.
Character theme tunes
- Next we have "Theme of ONE PUNCH MAN", essentially Saitama's Leitmotif.
- The pleasant acoustic version of "Theme of ONE PUNCH MAN".
- The Ballad version of "Theme of ONE PUNCH MAN", used for emotional moments of the series.
- Season two continued to make new versions of the theme in the form of a simple piano version and a string quartet version.
- The Cyborg Fights, the fighting theme for Genos. It got a remix for season two, which is basically the same song but with more electric guitar than ever.
- JUSTICE RIDER, the theme of everyone's favorite bicyclist, Mumen Rider!
- Metal Bat's brutal, thumping theme: Metal Bat.
- Bang's theme in Season 2, titled simply Martial Arts, truly evokes the image of a seasoned master.
- The aptly-titled Fake Star is King's theme. It starts out badass and menacing, but evolves into a chill and somewhat goofy guitar around the middle, perfectly representing his character.
- Rapid Speed, the theme for Suiryu's battles, is fittingly energetic and powerful.
- Sonic, the Leitmotif of... Speed O' Sound Sonic. Who would have guessed?
- Wet My Scales, the ominous theme of the first truly threatening villain in the series, the Deep Sea King.
- Dark Energy, the theme of the overall invasion force and the battle theme of Boros, the series' first threat not just to Earth but to Saitama as well.
- The Ruler, the climactic theme used when Saitama breaks Boros' Power Limiter armor and his true potential is unleashed, giving rise to the first challenging match Saitama has during the series. "HERE I COME!"/"IT IS TIME!"
- Garou's theme, I'm A Monster, serves as his Theme Music Power-Up for whenever he's about to pull off something insane - which is pretty much every scene he's in.
Other background music
- The tense Monster plays during several fight scenes, most notably the duel between Saitama and Genos.
- The ominous Kowa plays during multiple suspenseful moments throughout the series, really setting in a dreadful feeling of something bad about to happen.
- The epic Hero Society notably plays during the introductory meeting of almost all the S-Class heroes at the Hero Association HQ.
- BATTLE!!! is used for... well, battles! This track is also known by fans as "Unbeatable" to reflect Saitama's winning track, sadly neither Beast King nor Carnage Kabuto can be reached to confirm such a claim.
- Accept Battles, the battle theme for Season 2, features intense guitar like Season 1's, but incorporates strings for a more heroic and grandiose sound as well.
- Crash plays only briefly during the Super Fight, but it's such an epic jam that it wouldn't be out of place in any other fight in the series.
- Never End, a heroic theme used for climactic battles such as Garou vs. Death Gatling's heroes and Genos vs. Elder Centipede.