There are several bands using this name:

1) Relentless is a Punk band from Joensuu, Finland.
2) Relentless is a Hardcore band from Sydney, Australia.
3) Relentless is a Grindcore band from Sweden.
4) Harnessing the power of old and new technology, Relentless -- based out of San Francisco, California -- produces aggressive, dramatic house music that comprises an intelligent balance between pop and underground styles. Using advanced theories in sound design and completely exclusive sources, Relentless is able to deliver what moves people. Reviews of their debut album, A Collection of Drama, shows that "the dance floor loves" them.

Outside of the studio, Relentless is a fresh new approach to live electronic music and deejaying. With the original concepts of stereo-typical mixing and deejaying, Relentless adds on-the-fly, live remixing and production for an unprecedented, peak-hour dance floor experience. Their style can best be described if you mixed Tocadisco, Erol Alkan, Kid Dub, Gabriel & Dresden, Daft Punk, Deep Dish, and Dirty South together.