| Acronym | Definition |
|---|
| BSI | British Standards Institution |
| BSI | Bundesamt für Sicherheit in der Informationstechnik (German: Federal Office for Security) |
| BSI | British Standards Institute (less common) |
| BSI | Build Security In (Strategic Initiatives Branch of DHS National Cyber Security Division) |
| BSI | Brief Symptom Inventory |
| BSI | Brain Science Institute (Japan) |
| BSI | Blue Square-Israel Ltd |
| BSI | Bloodstream Infection |
| BSI | Banca della Svizzera Italiana |
| BSI | Body Substance Isolation (transmittable disease protection) |
| BSI | Boreal Songbird Initiative |
| BSI | British Society for Immunology |
| BSI | Big Sky Institute (Montana State University) |
| BSI | Baker Street Irregulars |
| BSI | Bromeliad Society International |
| BSI | Broadcast Software International |
| BSI | Botanical Survey of India |
| BSI | Bob Smith Industries |
| BSI | Bureau of Special Investigations |
| BSI | Brilliance Semiconductor, Inc. |
| BSI | Body Shop International (Brighton, UK) |
| BSI | Building Stone Institute (New York, New York) |
| BSI | Bina Sarana Informatika |
| BSI | Benefit Services, Inc. |
| BSI | Business Strategies International |
| BSI | Brand Science Institute |
| BSI | Business Software, Inc. |
| BSI | Bergensstudentenes Idrettslag (Norwegian: Students in Bergen's Sportsclub) |
| BSI | Baltic Scientific Instruments (Riga, Latvia) |
| BSI | Bioinformatics Solutions, Inc. (Waterloo, Canada) |
| BSI | Bioinformatics Summer Institute (University of Minnesota) |
| BSI | Behavioral Science Institute |
| BSI | Built-In Systems Interface (automotive) |
| BSI | Badger State Industries (Madison, WI) |
| BSI | Bankruptcy Services, LLC |
| BSI | Building Service, Inc. (Milwaukee, WI) |
| BSI | Bureau of School Improvement (Florida) |
| BSI | Booking Services International (Europe) |
| BSI | Bridge Software Institute (University of Florida) |
| BSI | Base Support Installation |
| BSI | Biological Sciences Initiative |
| BSI | Basic Services Interface |
| BSI | Brewer Science, Inc. |
| BSI | Boeing Services International |
| BSI | BioSciences Institute (Ireland, UK) |
| BSI | Building Science Insight |
| BSI | British Suzuki Institute (UK) |
| BSI | Borescope Inspection (gas turbine) |
| BSI | Bodyguard Services International Ltd (UK) |
| BSI | Business Solution Integration (Hitachi) |
| BSI | Billing Solutions, Inc. |
| BSI | Biotechnical Services, Inc. |
| BSI | Business Strategy, Inc. |
| BSI | Base Station Interface |
| BSI | Braggstar S-Industrial (Coherent, Inc laser) |
| BSI | Broadcast Services, Inc. |
| BSI | Biological Specimen Inventory System (Information Management Services, Inc.) |
| BSI | Bollinger Shipyards, Inc (Lockport, Louisiana) |
| BSI | Bankruptcy Services, Inc. |
| BSI | Button Systems, Inc. (Castleton, VT) |
| BSI | Biophotonic Solutions, Inc. |
| BSI | Business Systems International Ltd (UK) |
| BSI | Basic Shipping Instructions |
| BSI | Biodiversity Surveys and Inventories (Smithsonian Institution program) |
| BSI | Bible Society in Israel (Jerusalem, Israel) |
| BSI | Building Standards Institute |
| BSI | Brain Symmetry Index |
| BSI | Biothane Systems International BV (Netherlands) |
| BSI | Blue Sky Institute (West Jordan, UT) |
| BSI | Business Support Incubator |
| BSI | Bi-Search International, Inc. |
| BSI | Battlefield Systems Institute |
| BSI | Bacterial Strain-Identification |
| BSI | Business Service Identity |
| BSI | Begin Segment Introducer |
| BSI | Business Standards Institution (UK) |
| BSI | Battlefield Systems Integration |
| BSI | Basic Safety Insulation |
| BSI | Ball Semiconductor Incorporated |
| BSI | Building Systems Institute |
| BSI | Basic Store Inventory |
| BSI | Business Synergetics International LLC |
| BSI | Branch and Store Instruction Address Register (CPU instruction) |
| BSI | Blue Star Interactive LLC |
| BSI | BUES/SvSig Interface |
| BSI | Balance System, Inc. (Seattle, WA) |
| BSI | Blood System Infection |