Arpa and ARPA may refer to:
- Arpa
- Arpa River in Armenia
- Areni, Armenia - formerly called Arpa
- Arpi, Armenia, also called Arpa
- Turkish for Akhurian River in Turkey and Armenia
- Italian for harp, sometimes used in scores
- Okay Arpa, Turkish karateka
- ARPA
- Advanced Research Projects Agency, renamed the Defense Advanced Research Projects Agency (DARPA) in 1972
- Advanced Research Projects Agency-Energy (ARPA-E), created in 2007, an agency within the US Department of Energy
- Agenzie Regionali per la Protezione Ambientale, the Italian environmental protection agencies.
- .arpa, top-level domain name, the acronym for the Address And Routing Parameter Area of Internet infrastructure
- Automatic Radar Plotting Aid
- Average Revenue Per Advertiser
- Archaeological Resources Protection Act of 1979
- ARPA – Aerolíneas Paraguayas
- ARPA – Association for Reformed Political Action