| Acronym | Definition |
|---|
| FIO | For Information Only |
| FIO | Fundusz Inicjatyw Obywatelskich (Polish: Civic Initiatives Fund) |
| FIO | Fournitures Industrielles de l'Ouest (French: Western Industrial Supplies) |
| FIO | Fusion-Io (stock symbol) |
| FIO | Fundusz Inwestycyjny Otwarty (Polish: Open-End Investment Fund) |
| FIO | File Input Output |
| FIO | Frame Input Output |
| FIO | Future Input Output |
| FIO | Fraction of Inspired Oxygen |
| FIO | Faecal Indicator Organism (sewage) |
| FIO | Florida Institute of Oceanography |
| FIO | Free In and Out |
| FIO | Federal Insurance Office (US Treasury Department) |
| FIO | Frais Institutionnels Obligatoires (French: Required Institutional Fees; Canada) |
| FIO | Figure It Out |
| FIO | Field Intelligence Officer (various locations) |
| FIO | First Institute of Oceanography (China) |
| FIO | Fire Investigation Officer (UK) |
| FIO | Future Insurability Option (insurance rider) |
| FIO | Future Is Ours |
| FIO | Faculty Information Officer (various universities) |
| FIO | Factory Installable Option |
| FIO | Financing and Insurance Operations |
| FIO | Fiber and Integrated Optics (journal) |
| FIO | Factory Integration Only |
| FIO | Frontier in Optics (Optical Society of America conference) |
| FIO | Field Information Officer |
| FIO | Fitness Institute Online |
| FIO | Foreign Intelligence Office/Officer |
| FIO | Force XXI Integration Office/Officer |
| FIO | Frequency In & Out |
| FIO | Flight Inspection Office (Federal Aviation Administration) |
| FIO | Federated Input/Output (electronics) |
| FIO | Forecast Informed Operations (California Department of Water Resources) |
| FIO | Fleet Intelligence Office (US Navy) |
| FIO | Fieldnetwork Input/Output |