| Acronym | Definition |
|---|
| CIU | Convergència I Unió (Partit Polític de Catalunya-España) |
| CIU | Columbia International University |
| CIU | Cyprus International University (est. 1997) |
| CIU | Common Interchange Unit |
| CIU | Customer Interface Unit |
| CIU | Chronic Idiopathic Urticaria |
| CIU | Customs and Immigration Union (Canada) |
| CIU | Central Interpretation Unit (UK) |
| CIU | Criminal Intelligence Unit |
| CIU | Crisis Intervention Unit |
| CIU | Criminal Investigations Unit |
| CIU | Computer Interface Unit |
| CIU | Categorical Industrial User (industrial wastewater discharge and pretreatment) |
| CIU | Center for International Understanding |
| CIU | Confederazione Italiana Unionquadri (Italian confederation) |
| CIU | Collective Investment Undertaking |
| CIU | Communications Interface Unit |
| CIU | Criminal Investigative Unit (police incident code; New Zealand) |
| CIU | Clinical Investigation Unit |
| CIU | Communications Intelligence Unit (various locations) |
| CIU | Centre d'Information sur l'Urbanisme (French: Urban Planning Information Center) |
| CIU | Club International Universitaire (French: International University Club; various locations) |
| CIU | Centralized Intake Unit |
| CIU | Canadian Institute of Underwriters |
| CIU | Cable Interface Unit |
| CIU | Channel Interface Unit |
| CIU | Cockpit Interface Unit |
| CIU | Central Interface Unit |
| CIU | Continuous Improvement Unit (various locations) |
| CIU | Controller Interface Unit |
| CIU | Comitato Italiano per l'Unicef (Italian) |
| CIU | Control Indicator Unit |
| CIU | Camera Interface Unit |
| CIU | Cryptologic Interface Unit |
| CIU | Care Initiation Unit (various organizations) |
| CIU | Community Information Utility (multimode network delivering information and entertainment) |
| CIU | College Information Unit |
| CIU | Crime Interdiction Unit |
| CIU | Cell Interface Unit |
| CIU | Converter Interface Unit |
| CIU | Sault Ste Marie, MI, USA - Chippewa County International Airport (Airport Code) |
| CIU | Central Injection Unit |
| CIU | Client Interface Unit (connecting an antenna control unit to a host's control unit) |