OLB may stand for:
- Olbia - Costa Smeralda Airport, IATA airport code
- Outside linebacker - a defensive position in American football and Canadian football
- Object Language Bindings - in computing
- Oldenburgische Landesbank - a German bank
- Online Bible
- Overpass Light Brigade - Series of illuminated (LED) signs used by activists and others. Each letter is held by a different person.