Cer or CER may refer to:
- Cer (mountain), a mountain in Serbia
- Cer (goddess), Greek goddess of violent death, one of the Greek primordial deities
- Canonical Encoding Rules, a set of ASN.1 encoding rules for formatting data in binary
- Centre for European Reform
- Certified Emission Reduction
- CER Computer, a series of early digital computers by Mihajlo Pupin Institute
- CER Crossover Error Rate, the level at which the number of false rejections equals the false acceptances. It is used to measure the accuracy of a biometric system.
- Cherbourg – Maupertus Airport, whose international airport code is CER
- Chinese Eastern Railway
- Classic Endurance Racing, a racing series for historic racing cars
- Closer Economic Relations, a free trade agreement between Australia and New Zealand
- Comparative Education Review, an education-related publication
- Comparative-Effectiveness Research
- Community of European Railway, European union of railway undertakings and infrastructure companies
- Conditioned emotional response
- Conference of European Rabbis
- Control event rate, a statistical value in epidemiology
- Commission for Energy Regulation, a Republic of Ireland energy regulator
- Carbon dioxide Evolution Rate, the net carbon dioxide observed in the exhaust gas of fermentation process, usually expressed in mmol C02 per liter of broth per hour.
- Cadet Evaluation Report, used in the U.S. Coast Guard