| NIIS | National Inhalants Information Service 
| Others |
| NIIS | National Injury Insurance Scheme
| Others |
| NIIS | National Insurance Inspection Services
| Others |
| NIIS | Nebraska Insurance Information Service
| Others |
| NIIS | Network Integration and Implementation Services
| Others |
| NIIS | Nigerian Institute for Industrial Security
| Others |
| NIIS | Non Intrusive Inspection Systems
| Others |
| NIIS | Nordic Institute for Interoperability Solutions
| Others |
| NIIS | Northshore International Insurance Services
| Others |
| NIIS | Nutrient Information Inquiry System
| Others |