IIF may refer to:
- IIf and ?:, the inline-if computing function
- Indirect immunofluorescence, one of several types of immunofluorescence
- Information Interchange Format (IIF), a record serialization format specified in ISO 2709, also published as ANSI Z39.2.
- Institute of International Finance (IIF), an association of international financial institutions
- International Indonesia Forum (IIF), an organisation which holds annual interdisciplinary seminars in Indonesia.
- International Institute of Forecasters (IIF), a nonprofit organization devoted to advancing the science of forecasting, and publisher of International Journal of Forecasting and Foresight: The International Journal of Applied Forecasting.
- Intuit Interchange Format, a file format used by Intuit's Quickbooks software