Arx, ARX, or ArX may refer to:

  • ARX (operating system), an operating system
  • Arx, the aristaless related homeobox gene and protein
  • Arx, Landes, a commune of the Landes d├ępartement in France
  • ArX (revision control), revision control software
  • ObjectARX, a software API for AutoCAD
  • Arx (Roman), a Roman citadel, and in particular:
    • The northern hump of the two forming the Capitoline Hill of ancient Rome
  • Arx Fatalis, a first person role-playing game developed by Arkane Studios in 2002
  • Arx, one of Lars Vilks sculptures