Roi may refer to:
People:
- Adenes Le Roi (c. 1240-c. 1300), French minstrel
- Alice Roi (born 1976), American fashion designer
- Roi Kahat (born 1992), Israeli footballer
- Roi Klein (1975-2006), major in the Israeli Defense Forces
- Roi Kwabena (1956-2008), Trinidadian cultural anthropologist and writer
- Roi George Partridge (1888–1984), American printmaker and teacher
- Rói Patursson (born 1947), Faroese writer and philosopher
- Roi Wilson (1921-2009), Royal Navy aviator
- "Le Roi" (French for "the King"), a nickname for French retired basketball player Antoine Rigaudeau (born 1971)
Other uses:
- Cú Roí, a king of Munster in Irish mythology
- USS Roi (CVE-103), a US aircraft carrier
- "Roi", a 1993 song by The Breeders in their album Last Splash
- Ro'i, an Israeli settlement in the West Bank
ROI may stand for:
- Return on Investment, used to evaluate the efficiency of an investment in finance and economics
- Reactive oxygen intermediate
- Risk of infection
- Region of interest
- Release of Information, in Health Information Management
- Republic of India
- Republic of Indonesia
- Republic of Ireland
- Royal Institute of Oil Painters