OSI

Places

Oblates of St. Joseph, a Roman Catholic Religious order that uses the postnominal initials O.S.I.
Open Source Initiative, an organization dedicated to promoting open source software
Open Society Institute, a private charitable foundation established by George Soros to promote open societies around the world
Open Society Institute-Baltimore, a locally based foundation that is part of Open Society Foundations
Open Space Institute, an organization that seeks to preserve scenic, natural and historic landscapes
Ordnance Survey International, a former subsidiary of the UK Ordnance Survey mapping agency
Ordnance Survey Ireland (Suirbhéireacht Ordanáis Éireann)
Otto-Suhr-Institut, the political-science institute of the Free University of Berlin

OSI Group, an American holding company of meat processors that service the retail and food service industries
OSI Pharmaceuticals, an American pharmaceutical company
OSI Restaurant Partners, the restaurant and entertainment group that includes Outback Steakhouse
OSI Systems, a company that manufactures security scanners and medical equipment based in California
OSIsoft, a privately held company that develops device connectivity software
Objective Systems Integrators, a company that provides monitoring software for communication networks
Open Systems International, an automation software vendor for the electric, petroleum, transportation and water industries
Officine Stampaggi Industriali, a defunct Italian coachbuilder
Ohio Scientific Inc. (also known as Ohio Scientific Instruments), a US microcomputer manufacturer 1975-1981

Office of Scientific Intelligence, former name of a department of the Central Intelligence Agency now called the Directorate of Science and Technology
Office of Strategic Influence, a former American government agency, part of the Department of Defense and focused on psychological warfare
Office of Special Investigations (disambiguation), a name shared by several government agencies
Office of Scientific Integrity, now United States Office of Research Integrity
Office of Special Investigation, a secret intelligence unit of Republic of Korea Air Force
Office of the Special Investigator Australia

Open Systems Interconnection, (ISO 7498) a joint ISO and ITU-T standard for computer networks and communication protocols
- OSI model, a layered description for communications and computer network protocol design
- OSI protocols
Open switching interval, a type of disconnect supervision in telecommunication
On-Site Inspection, an advanced measure technique combining several methods, especially used in order to detect nuclear tests

OSI (band), an American progressive rock supergroup named after the former Office of Strategic Influence government agency
- Office of Strategic Influence (album), the 2003 debut album by the band OSI
Origin Systems, a former United States computer game developer
Orchestra della Svizzera Italiana, an orchestra in southern Switzerland in the city of Lugano which is in the canton of Ticino

Office of Scientific Intelligence a fictional United States government agency in several television programs and movies;
Office of Secret Intelligence, a fictional United States government secret agency in the animated series The Venture Bros.

Order of the Star of Italy, an order of chivalry
Official sector involvement, in sovereign debt restructuring deals, as opposed to private sector involvement
Options Symbology Initiative, a plan to change the way that exchange-traded options are named in option symbol
Out-of-Station Interchange, a pedestrian change between two London Underground stations that allows continuity as part of one chargeable journey