NSIU
| Acronym | Definition |
|---|---|
| NSIU | Navigation Switching Interface Unit |
| NSIU | Norges Svalbard- og Ishavs-Undersokelser |
| NSIU | Nationwide Special Investigations Unit (Schaumburg, IL) |
| NSIU | Navigation System Interface Unit |
| NSIU | Non-Significant Industrial User |
| NSIU | National Security Industry Union (UK) |