| NIWA | Namibian Information Workers' Association 
| Others |
| NIWA | National Inland Waterways Authority
| Others |
| NIWA | National Institute for Water and Atmospheric
| Others |
| NIWA | National Institute for Water and Atmospheric Research, New Zealand
| Others |
| NIWA | National Institute for Weather and Atmospheric
| Others |
| NIWA | National Institute of Water and Atmospheric
| Others |
| NIWA | Naval Information Warfare Activity
| Others |
| NIWA | Nigerian Inland Waterway Authority
| Others |
| NIWA | Nigerian Internet Webmasters Association
| Others |
| NIWA | Nintendo Independent Wiki Alliance
| Others |
| NIWA | Northwest Independent Writers Association
| Others |