CYS or Cys may refer to:

• Cysteine, an amino acid abbreviated Cys

• Cheyenne Regional Airport, Wyoming, United States, IATA and FAA LID airport code

• Cathays railway station, Cardiff, Wales, station code

• California Youth Symphony, a San Francisco Bay Area symphony orchestra for young musicians

• Cyprus Organization for Standardization, the Cyprus national standardization body

• Cys Kurland, footballer who played for the South African national side in 1947

See also

• Cys-la-Commune, a French commune