ISF may stand for:
- Impôt de Solidarité sur la Fortune, a French wealth tax
- Incremental sheet forming
- Ingenieurs Sans Frontieres (Engineers Without Borders)
- Internal Security Forces, of Lebanon
- International Softball Federation
- International School of Florence
- International Snowboard Federation
- Information Security Forum, an international information security best practices organization
- Île Sans Fil, a community wireless network based in Montreal, Canada
- Internationale Schule Frankfurt Rhein-Main
- Lexus IS F
- Ink Serialized Format, a vector image file format from Microsoft
- Importer Security Filing