Ri

RI or ri may refer to:

• Ri, a common Korean surname, a variant romanization of Lee
• Rí (rig), an ancient Gaelic word meaning "king"
• Ri, a proposed gender-neutral pronoun for gender reform 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

• 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)

• Ri, an augmented second in solfege, used in music education
• Ri, a representation of the second svara in Indian classical music
• Russia Insider, a news website

• 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)
• TVRI (Televisi Republik Indonesia), a state-owned, public broadcasting television network in Indonesia
• Tigerair Mandala (IATA airline designator RI)
• Italian Radicals, a political party in Italy

• 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

• 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