| Acronym | Definition |
|---|
| FUN | Function |
| FUN | Future University Hakodate (est. 2000; Japan) |
| FUN | Faculty for Undergraduate Neuroscience |
| FUN | Future University Network (Jordan) |
| FUN | Formula Unit (chemistry) |
| FUN | Families United Network (various locations) |
| FUN | Friends of the United Nations |
| FUN | Future Ubiquitous Networks (France) |
| FUN | Finally Understanding Nothing (Gary Busey quotation) |
| FUN | Financial Underwriters Network |
| FUN | Finding Urban Nature (Seattle Audobon Society children's program) |
| FUN | Florida United Numismatists, Inc. |
| FUN | Friendship Udankhatola (Indian rural exposure camp) |