This is a disambiguation page; if one followed a link here, one might want to adjust that link.
ER is an acronym which refers to:
- In cell biology, the endoplasmic reticulum, which is either rough or smooth
- the "emergency room" in a hospital, wherein victims arrive in emergency situations (usually by ambulance).
- a popular NBC medical drama, named ER for emergency room
- Eritrea (ISO country code)
- Elizabeth Regina (Elizabeth the Queen); see Elizabeth I of England and Elizabeth II of the United Kingdom.