RI

RI or ri may refer to:

People

 * Ri, a common Korean surname, a variant romanization of Lee
 * Rí (rig), an ancient Gaelic word meaning "king"
 * Ri (pronoun), a gender-neutral pronoun in Esperanto
 * RI, an initialism of Rex Imperator (king-emperor) or Regina Imperatrix (queen-empress), used by those British monarchs who were rulers of both the United Kingdom and the Indian Empire

Places

 * Ri (administrative division), an administrative unit in both North Korea and South Korea
 * Ri, Orne, a commune of the Orne département in France
 * RI, abbreviation of either the Republic of Indonesia or, in the Indonesian language, Republik Indonesia
 * Rhode Island, a state within the US (postal abbreviation RI)

Arts and media

 * Ri, an augmented second in solfege, used in music education
 * Ri, a representation of the second svara in Indian classical music
 * Russia Insider, a pro-Kremlin news and propaganda website

Businesses and organizations

 * Raffles Institution, a school in Singapore
 * Refugees International, an international humanitarian organization
 * Rehabilitation International, an international disability rights organization
 * Rotary International, international organization of business and professional leaders focused on non-political and non-sectarian humanitarian service
 * Royal Institution of Great Britain, an organisation devoted to scientific education and research
 * Royal Institute of Painters in Water Colours, a society in the Federation of British Artists
 * Chicago, Rock Island and Pacific Railroad (reporting mark RI)
 * Tigerair Mandala (IATA airline designator RI)
 * Italian Radicals, a political party in Italy

Science, technology, and mathematics

 * Ri (prefix symbol), a binary unit prefix symbol
 * Referential integrity, a database concept
 * Refractive index of an optical medium (in physics/optics) is a number that describes how light propagates through that medium
 * Arterial resistivity index, a measure of pulsatile blood flow
 * Ring Indicator, a signal in the RS232 serial communications standard
 * Rhombicosahedron, a polyhedron, by Bowers acronym
 * Residual income, a financial profitability measure of a company
 * Reputation Institute, a research and insights company that analyzes the reputation of corporations and places
 * Rapid intensification, a phenomenon in which the wind speed of a tropical cyclone increases dramatically in a short period of time
 * Research infrastructure, national or international infrastructure open to scientists (e.g. CERN)
 * Research institute, an establishment founded for doing research

Other uses

 * Ri (cuneiform), a cuneiform sign
 * Ri (kana), a Romanization of the Japanese kana り and リ
 * Ri, a unit of measurement in Japan and Korea related to the Chinese li
 * Rock Island District, a commuter rail line on Chicago's Metra (abbreviated as RI on maps and schedules)