OCI may refer to:
- Companies
- Orascom Construction Industries, Egyptian conglomerate
- OCI (company), a diversified Korean conglomerate and worlds largest polysilicon producer
- Computing
- Open Catalog Interface
- Oracle Call Interface
- Institutes
- Ontario Cancer Institute
- Open Constitution Initiative
- Ottawa Collegiate Institute
- Oakwood Collegiate Institute
- Organisations
- Organisation Communiste Internationaliste (France)
- Organizzazione Comunista Internazionalista (Italy)
- Outpost Centers International, an independent Seventh-day Adventist organization
- Other
- Organizational Conflict of Interest
- Overseas Citizen of India
- the Occitan language
- Other Comprehensive Income (accounting)
- The Office of Criminal Investigations, part of the US Food and Drug Administration