OEC may refer to:
- Offshore Energy Center, sponsor of the Ocean Star Offshore Drilling Rig & Museum in Galveston, Texas, United States
- Old Earth creationism, a term for several types of creationism
- Olfactory ensheathing cells, a type of glial cell found in the nervous system
- Ordre des Experts-Comptables, French association of chartered accountants
- Oregon Environmental Council, an American environmental organization
- Orion Expedition Cruises, Australian based luxury expedition cruise line
- Orissa Engineering College, a technical institution in Bhubaneswar, Orissa, India
- Osborn Engineering Company, a former British manufacturer of motorcycles
- Otis Elevator Company, an American company that manufactures vertical transportation systems
- Outdoor Emergency Care, a course for certification of first aid in non-urban situations
- Oxygen evolving complex, a water oxidizing enzyme
- .OEC, the file format for OE-Cake!