CYS

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