ORS may refer to:
- Oxygen reduction system
- Ocean Rowing Society
- Oculo-respiratory Syndrome
- Office of Rehabilitation Services
- Office of Recovery Services
- Office of Retirement Services
- Old Red Sandstone
- Olfactory Reference Syndrome
- Omnificent Role-playing System
- Oneida Research Services
- Online Radio System
- Online Resource Scheduler
- Operational Research Section of RAF Bomber Command
- The Operationally Responsive Space Office within the United States Department of Defense
- Oral rehydration salt or oral rehydration solution
- The IATA airport code for Orpheus Island Resort Waterport in Queensland, Australia
- The FAA airport code for Orcas Island Airport, Eastsound, Washington
- Ordered Recovery Systems, LLC
- Oregon Revised Statutes
- Organic-Rich Shales
- Orlando Riva Sound
- Orthopaedic Research Society
- Output Record Separator
- Ovarian Remnant Syndrome
- Overseas Research Scholarship
- Overseas Research Student
- Optical Response Sheet
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