Phat pants or phatties are usually made of denim but can be made of any material, and are fitted at the waist, but get wider down the legs all the way to the ground where they enclose the feet due to their width. Phat pants are usually worn by ravers and can be used as a visual identifier. Ravers will often customise their phat pants by covering them with reflective materials of their own design. The pants are worn at rave parties, where the glow of the reflectors illuminates people's legs while they dance. It is usually worn by people who listen to hardcore, hardstyle, and other hard genres of electronic music.

Phat Pants were first produced in Vancouver in 1995 by Laramie^{[disambiguation needed ]}. The head designer was Noel Steen.

UV reactive tape is usually sewn or glued onto phat pants. When light (usually UV rays from the sun or black light) hits the tape, the tape absorbs the UV energy and emits visible light, causing the tape to "glow". Many ravers and shufflers who wear phat pants purchase small portable UV lights as they can point it at the phat pants giving them an intense "glow" as seen in some videos on YouTube.