| Acronym | Definition |
|---|
| REI | Recreational Equipment, Inc. |
| REI | Real Estate Investment |
| REI | Real Estate Investing |
| REI | Restricted Entry Interval (pesticides) |
| REI | Ricoh Electronics, Inc. (Tustin, CA) |
| REI | Real Estate Institute (various locations) |
| REI | Research and Educational Institute (various organizations) |
| REI | Recommended Exposure Index (camera feature) |
| REI | Renewable Energy Initiative |
| REI | Reproductive Endocrinology and Infertility |
| REI | Reset Indication |
| REI | Remote Error Indicator |
| REI | Request for Expressions of Interest |
| REI | Reykjavik Energy Invest (Iceland) |
| REI | Rosendin Electric, Inc. (various locations) |
| REI | Real Economic Impact (tour; various locations) |
| REI | Régiment Etranger d'Infanterie (French: Foreign Infantry Regiment) |
| REI | Revue d'Economie Industrielle (French: Journal of Industrial Economics) |
| REI | Research, Evaluation and Information (various organizations) |
| REI | Reentry Interval |
| REI | Reliant Energy, Inc. |
| REI | Remote Error Indication |
| REI | Research Engineers International |
| REI | Ross Eye Institute (Buffalo, NY) |
| REI | Ripple Effects Interactive (Pittsburgh, PA) |
| REI | Recherche Exploratoire et Innovation (French: Exploratory Research and Innovation) |
| REI | Recursos Electrónicos de Información (Spanish) |
| REI | Real Estate Innovator |
| REI | Réseau Economie Internationale (French: International Economics Network; Canada) |
| REI | Radio España Independiente (Spanish: Radio Free Spain) |
| REI | Recognition Equipment Incorporated |
| REI | Request for Engineering Information |
| REI | Renewable Energy Island |
| REI | Rad Elec Inc. |
| REI | Rapid Enzymatic Indicator |
| REI | Rotating Equipment Initiative |
| REI | Recovered Energy Inc (Pocatello, ID) |
| REI | Research Equipment Incorporated |