Otr may refer to:
- Ótr, a mythical dwarf
- Otaara, a plant genus
OTR may also refer to:
in science:
- Oxygen transmission rate, a measure of packaging permeability
- Transition radiation, a type of electromagnetic radiation
In broadcasting:
- Old-time radio, a broadcasting era
- Off The Record (TSN TV series), a sports talk show
In music:
- On The Rocks (band), a rock group of international artists
- Over the Rhine (band), an American folk group
- Otierre, an Italian hip hop group
in other uses:
- Off-the-Record Messaging, an instant messaging encryption system
- On the run (finance), a status of financial securities or contracts
- Organisation and Technology Research, an information technology company
- Over-the-Rhine, a neighborhood in Cincinnati, Ohio, United States
- On the Run (convenience store), a retail chain
- Coto 47 Airport, in Costa Rica
- Off-the-road, a type of tire
- Occupational Therapist Registered, the title of an occupational therapist who has passed the National Board for Certification in Occupational Therapy's NBCOT-OTR examination