ER
ER may stand for:
- the endoplasmic reticulum (a cellular body), which is either rough or smooth
- an acronym for the "emergency room" in a hospital, wherein victims arrive in emergency situations (usually by ambulance).
- ER is a popular NBC medical drama, referring to the above acronym
- Eritrea (ISO country code)
- Elizabeth Regina (Elizabeth the Queen); see Elizabeth I of England and Elizabeth II of the United Kingdom.
