OPI may refer to:
Organizations Order of Perpetual Indulgence or Sisters of Perpetual Indulgence The Office of Police Integrity, Victoria, Australia
Science and technology Open Payment Initiative Ocular protection index
Places Opi, Abruzzo, a comune in Italy Opi (archaeological site), Enugu State, Nigeria
Other uses Over the phone interpreting Oral Proficiency Interview OPI Products, a US nail polish manufacturer Opi, an Igbo musical instrument Oremus Pro Invicem, Latin for Let us Pray for each other (see List of Latin phrases (O))