EOR could refer to:
- Earth Orbit Rendezvous, a proposed method for space missions to the Moon
- Electro-optic rectification, a non-linear optical process
- Enhanced oil recovery, a term in petroleum production
- Epping Ongar Railway, a heritage railway in England
- European ordering rules, a standard to put words or names into sequence
- Exclusive or, the exclusive disjunction in logic
- Epoch of Reionization, a process that reionized matter in the universe.
- Economics of Religion, a field of study using economics to understand religion
- the character Eeyore from the Winnie the Pooh series.