RI (disambiguation)

RI may refer to any of the following:

• Republic of Indonesia
• Rhode Island, an American state
• Aquidneck Island (sometimes called Rhode Island, not to be confused with the state)
• Rijeka, a city
• Rotary International
• Rock Island railroad reporting mark
• Mandala Airlines IATA airline designator
• Raffles Institution, a prestigious school in Singapore
• Reference Implementation (computing), a software package
• Referential integrity, a concept in computer databases
• Refractive index
• Refugees International, an international humanitarian organization
• Rehabilitation International, an international disability rights organization
• Rex Imperator or Regina Imperatrix, the suffix used by British monarchs as Emperors of India
• The Royal Institution of Great Britain
• Royal Institute of Painters in Water Colours, a society in the Federation of British Artists
• Ring Indicator, a signal in the RS232 serial communications standard
• Repubblica Italiana
• Ri (administrative division)
• Ruby Information, documentation tool that is part of the Ruby (programming language) toolkit

Ri may refer to any of the following:

• A traditional unit of length in both Korea (리, ri) and Japan (里, ri) based upon the Tang Dynasty Chinese li (里, lǐ or 市里, shì lǐ)
• Ri (kana), a Romanization of the Japanese kana り and リ
• An augmented second in Solfege
• The commonly used and known representation of the second Swara — "Rishabam" (Carnatic) or "Rishab" (Hindustani classical music) in the Indian Classical Music form
• Riism, a neologism used as a gender-neutral pronoun in Esperanto
• Ri, Orne, a commune of the Orne département, in France
• Rí, the ancient Gaelic word meaning King
• Isaac ben Samuel, known as the "Ri", a 12th-century French tosafist and Biblical commentator
• Rhombicosahedron