Trey could refer to a nickname for those who are the third of their name. For example, this is William Henry Gates III's nickname within his family. Most of the persons listed here are named Trey for this reason:

• Trey Anastasio, an American guitarist, composer and singer, lead guitarist of Phish
• Trey Azagthoth, a guitarist for death metal band Morbid Angel
• Trey Brewer, competitive bodybuilder, NPC Bodybuilding Championships Overall Winner
• Trey Gunn, a member of the band King Crimson
• Trey Junkin, a former American football player
• Trey Parker, co-creator of South Park, along with Matthew Stone.
• Trey Sides, an R&B singer
• Trey Spruance, an American musician
• Trey Teague, an American football player
• Trey of Triforia, a character in Power Rangers: Zeo
• Trey, Vaud, a commune in Vaud, Switzerland
• Trey Wingo, an American sportscaster
• Trey Lewis, an NFL defensive tackle for the Atlanta Falcons.
• Trey Lewis, female tennis player from 1979–1986.
• Trey Smith, son of actor and singer Will Smith.
• Trey A. Corrales, Sergeant First Class in the U.S. Army
• Trey Atwood, fictional character on The OC
• Trey Bruce, country singer

Trey could also mean:

• Tré, a nickname used in basketball to express a three point field goal
• Standard Anglo-American playing cards of rank three, as in "the trey of hearts" (3♥)