EOR could refer to:

• Earth Orbit Rendezvous, a proposed method for space missions to the Moon
• Electric orbit raising, a method in space technology of reaching higher orbits by means of electric propulsion
• Electro-optic rectification, a non-linear optical process
• Employer of record, a co-employment company
• 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 IOC country code for the IOC Refugee Olympic Team at the 2020 Summer Olympics
• the character Eeyore from the Winnie the Pooh series.