| Acronym | Definition |
|---|
| ISO | In Search Of |
| ISO | [not an acronym] common short name for the International Organization for Standardization; also see Iso- prefix |
| ISO | International Standards Organization (common, but incorrect) |
| ISO | Instead Of |
| ISO | International Organization for Standardization |
| ISO | In Support Of |
| ISO | International Student Organization |
| ISO | Isolation (sports play-calling, especially basketball) |
| ISO | Isochronous (band) |
| ISO | Information Security Officer |
| ISO | Information Security Operations (various organizations) |
| ISO | Isometric |
| ISO | Independent System Operator |
| ISO | Isotope |
| ISO | Isolated Power (baseball statistic) |
| ISO | Incentive Stock Option |
| ISO | Infrared Space Observatory |
| ISO | International Socialist Organization |
| ISO | Isoproterenol |
| ISO | Insurance Services Office, Inc. (CMSP and PLSP statistics are reported to this rate making organization) |
| ISO | Insurance Service Organization |
| ISO | Indianapolis Symphony Orchestra |
| ISO | International Student Office (various universities) |
| ISO | Internal Sales Order |
| ISO | International Science Olympiad |
| ISO | Independent Sales Organization |
| ISO | Imperial Service Order |
| ISO | Independent Service Organization |
| ISO | Indian Student Organization |
| ISO | Independent Sales Office |
| ISO | Imamia Students Organization (Pakistan) |
| ISO | Information Systems Office |
| ISO | Information Systems Officer |
| ISO | International Standards Organization |
| ISO | Interstedelijk Studenten Overleg (Netherlands student organization) |
| ISO | Illinois Symphony Orchestra |
| ISO | Istanbul Sanayi Odasi |
| ISO | Information Services Organisation (various locations) |
| ISO | Installation Safety Office |
| ISO | Intensive Supervision Officer |
| ISO | Isolierverglasung (German: insulating glass) |
| ISO | Intermediary Services Organization |
| ISO | Independent Study Online (distance learning) |
| ISO | Inspection of Services |
| ISO | Intraseasonal Oscillation |
| ISO | Industry Standards Organization (IEEE-ISTO) |
| ISO | International Society of Organbuilders |
| ISO | Insurance Support Organization |
| ISO | International Scholar Office (University of California, San Diego) |
| ISO | Isochronal Inspection (USAF; scheduled maintenance for aircraft) |
| ISO | Inspection of Supplies |
| ISO | Intermarket Sweep Order (finance) |
| ISO | Kinston, NC, USA (Airport Code) |
| ISO | Imaging Spectrometric Observatory |
| ISO | Imperial Symphony Orchestra |
| ISO | Impuesto de Solidaridad (Guatemala) |
| ISO | Integration Staff Officer |
| ISO | Israel Symphony Orchestra (est. 1988) |
| ISO | Isochronical Inspection (USAF; phase of aircraft maintenance) |
| ISO | Intelligence and Security Office(r) |
| ISO | International Satellite Organization |
| ISO | Instructional Services Office (various schools) |
| ISO | Internal Service Order |
| ISO | Institutional Support Office |
| ISO | Installation Support Office |
| ISO | Installation Supply Officer |
| ISO | Internet Sales Outlet |
| ISO | Open System Interfacing |
| ISO | Istanbul Sanayi Odasý (Turkish: Istanbul Chamber of Industy) |
| ISO | Independent Scholar Option |
| ISO | Immigrant Serving Organization (Canada) |
| ISO | Interservice Support Office |
| ISO | International Switch Operations |