CSIO

CSIO may refer to:


 * Central Scientific Instruments Organisation, an Indian national laboratory dedicated to research, design and development of scientific and industrial instruments
 * Centre for Study of Insurance Operations, the Canadian property and casualty insurance industry's nonprofit association of insurers, brokers and software providers
 * City State of the Invincible Overlord, a 1976 Judges Guild product that was the first published fantasy role-playing game city setting
 * Concours de Saut International Officiel, a ranking system for the equestrian competition show jumping