"Rez" is a non-album track by British electronic music group Underworld, originally released in 1993 in the UK.
It became a popular club hit and live track in Underworld's sets, despite the fact it could not be found on an album.
The first promo release of the single was pressed onto pink vinyl, and is highly collectible as it has an exclusive non-album track, "Why, Why, Why".
The more common release has the single "Cowgirl" as its b-side.
This version also received a limited white vinyl pressing in the US.