Arx, ARX, or ArX may refer to: ARX (Algorithmic Research Ltd.), a digital security company ARX (gene), Aristaless related homeobox ARX (operating system), an operating system ArX (revision control), revision control software Arx (Roman), a Roman citadel, and in particular: The northern hump of the two forming the Capitoline Hill of ancient Rome Arx, Landes, a commune of the Landes département in France Arx Fatalis, a first person role-playing game developed by Arkane Studios in 2002 Arx, a sculpture by Lars Vilks Americas Rallycross Championship, also known as ARX Rallycross Add-Rotate-XOR; see block cipher See also Beretta ARX160, an assault rifle ObjectARX, a software API for AutoCAD