- API stands for A Pleasing Interface
- API stands for A Positive Image (various organizations)
- API stands for A Pressen Interaktiv (Norwegian: Digital Media)
- A/PI stands for Ab initio Perturbed Ion (quantum classification method)
- API stands for Absolute Position Indication
- API stands for Academic Performance Index
- API stands for Academic Programs International (Austin, TX)
- API stands for Accelerated Performance Improvement
- API stands for Accountable Property Inventory
- API stands for Acquisition Program Integration
- API stands for Active Pharma Ingredient
- API stands for Active Pharmaceutical Ingredient
- API stands for Administración Portuaria Integral (Mexico)
- API stands for Advanced Passenger Information
- API stands for Advanced Pharmaceutical Ingredients
- API stands for Advanced Photonix, Inc. (various locations)
- API stands for Advanced Polygraph Institute (Australia)
- API stands for Advanced Product Information (various businesses)
- API stands for Advertisers Product Index
- API stands for Aerial Photographic Interpretation (American Society of Photogrammetry and Remote Sensing)
- API stands for After Project Initiation
- API stands for Age Participation Index (UK)
- API stands for Agfa and Picker International
- API stands for Agricultural Price Index
- API stands for Air Photo Interpretation
- API stands for Air Pollution Index
- API stands for Air Position Indicator
- API stands for Aircraft Platform Interface
- API stands for Aircrew Position Indicator (USAF)
- API stands for Aisne Plastique Industrie (French: Aisne Plastic Industry; Aisne, France)
- API stands for Ajax Paving Industries (various locations)
- API stands for Alabama Polytechnic Institute
- API stands for Alagus Printer Installer (software)
- API stands for Alaska Psychiatric Institute
- API stands for Alert Process Improvement (Sprint)
- API stands for Alice Paul Institute (Mount Laurel, NJ, USA)
- API stands for Alliance for the Polyurethanes Industry
- API stands for Allocation de Parent Isolé (French: Single Parent Allowance)
- API stands for Alpha Processor, Inc. (Samsung)
- API stands for Alphabet Phonétique International (French: International Phonetic Alphabet)
- API stands for Alt Preset Insane (MP3 encoder preset)
- API stands for American Pacific Industries (Valencia, CA)
- API stands for American Pain Institute
- API stands for American Paper Institute
- API stands for American Petroleum Institute
- API stands for American Pirate Industries
- API stands for American Prepaid Legal Services Institute
- API stands for American Press Institute
- API stands for American Products, Inc. (Florida)
- API stands for American Professional Institute (Georgia)
- API stands for Analytical Profile Index (microbiology)
- API stands for Anderson Packaging, Inc. (Rockford, IL)
- API stands for Angus Productions Inc.
- API stands for Animal Protection Institute
- API stands for Ankle Pressure Index
- API stands for Année Polaire Internationale (French: International Polar Year; research project)
- API stands for Announcement of Public Interest
- API stands for Annual Physical Inventory
- API stands for Annual Plan for Instruction
- API stands for Annual Premium Income
- API stands for Annual Price Increase
- API stands for Anonima Petroli Italiana SpA (Rome, Italy)
- API stands for Ansal Properties Infrastructure (India)
- API stands for Antecedent Precipitation Index
- API stands for Anti-Poverty Initiative (various locations)
- API stands for Apple Learning Interchange
- API stands for Appleton Papers, Inc. (Appleton, WI)