ECU may refer to:
- Automotive terms
- Electronic control unit, a generic term for any embedded system that controls one or more of the electrical systems or subsystems in a motor vehicle
- Engine control unit, one type of electronic control unit that manages an engine's operation
- Currencies
- European Currency Unit, a former basket of the currencies of the European Community, precursor to the euro
- Écu, the name of several French coins
- Universities
- East Carolina University in Greenville, North Carolina, USA
- East Central University in Ada, Oklahoma, USA
- Edith Cowan University in Perth, Western Australia, Australia
- Other
- Ecuador, which is abbreviated to contain the first three letters: ECU
- Extensor carpi ulnaris, a muscle of the forearm
- Extreme close-up, a cinematographic term
- ÉCU The European Independent Film festival
- A "Elastic Compute Unit" (ECU), measure of computer power specific to the Amazon Elastic Compute Cloud