ISO may refer to:

• International Organization for Standardization, an international standard-setting body
  • List of ISO standards including:
    • ISO 5800:1987, for Film speed (or ISO speed)
    • ISO 9000, for quality management systems
    • ISO image (.iso), is a disk image of an ISO 9660 file system
• Infrared Space Observatory, a space telescope designed and operated by the European Space Agency
• Incentive stock option
• Imperial Service Order, an award in the British honours system
• Independent System Operator, an organization that coordinates a regional wholesale electricity market in the United States
• International Science Olympiad, a group of worldwide annual competitions
• Indianapolis Symphony Orchestra
• Independent sales organization, administers merchant and/or cardholder servicing
• International Sugar Organization, devoted to improving conditions on the world's sugar market
• Insurance Services Office, in the United States
• International Socialist Organization, which is active in the United States
• International Socialist Organisation (Australia)
• Kinston Regional Jetport, IATA code ISO
• "In Search Of", Online jargon
• Inside-out roll, a type of sushi roll with the rice on the outside of the nori, Japanese name Uramaki.
• I.S.O., an EAI-band from Japan, with Yoshihide Otomo, Sachiko M and Yoshimitsu Ichiraku as musicians.

Iso may also refer to:

• Isoprenaline, an adrenergic agonist
• Iso (record label), created by David Bowie after he left Virgin Records
• Iso Rivolta, Italian car brand that went bankrupt in 1974

iso- is a prefix from the Greek isos, meaning "equal." It is used primarily in scientific and technical terms, such as isometric, isotonic, and isonomic.

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