ORP may refer to:
- Oxidation reduction potential, the tendency of a chemical species to acquire electrons and thereby be reduced
- Open Relevance Project, data and tools to compare the search relevancy performance of search engines
- Operational Ration Pack, a combat ration used by the British Armed Forces
- O'Reilly Raceway Park at Indianapolis, a motorsports racing facility in Indianapolis, Indiana
- Orpington railway station, in southeast London, England
- Okręt Rzeczypospolitej Polskiej, a traditional ship prefix in the Polish Navy meaning Vessel of the Republic of Poland