IS may refer to:

• Book of Isaiah, a biblical text
• Is (novel), a novel by Joan Aiken
• i"s, a manga by Masakazu Katsura
• iS (manga), a manga by Chiyo Rokuhana
• Infinite Stratos, a Japanese light novel series

• is (album), a 1969 album by jazz pianist Chick Corea
• is, a 2012 album by Canadian pop band Hey Ocean!
• iS – internal section, a video game developed by Square

• Intermediate school, education between primary and secondary schools areas, also known as middle school
• Ilta-Sanomat, a newspaper in Finland
• Intelligent Systems, a first-party video game developer and internal team of Nintendo
• International Socialists (disambiguation), several Trotskyist political organizations
• Investment—Saving, a curve in the IS/LM model of economics
• IRS Airlines (IATA code)
• Island Airlines (IATA code)

• Is, the third-person singular present tense of the English language verb "to be", frequently used as a copula
• Icelandic language (ISO 639-1 alpha-2 code)
• International Sign, a pidgin sign language

• Is (rune) (ᛁ), a rune of the Anglo-Saxon fuþorc

• Island (Is.), any piece of land surrounded by water
• Iceland (ISO 3166-1 alpha-2 country code)
• Israel (NATO country code)
• Hīt, or Is, an Iraqi town on the Euphrates River
• Ys or Is, a mythical city of Brittany
• Iași County, Romania, (vehicle registration code)
• Inverness TMD, a railway traction maintenance depot (depot code)
• Province of Isernia, Italy (vehicle registration code)

• Immune system, organic mechanisms that protect against disease
• Immunosuppression
• Importance sampling, a statistical technique for estimating properties of a particular distribution
• Infrasound, sound frequencies below the human range of hearing
• Insertion sequence, a short DNA transposable element
• Intersex, an organism with sex characteristics neither exclusively male nor female

• .is, the Internet country-code top-level domain for Iceland
• Information science, the study of data collection, manipulation, and dissemination
• Information systems, organizations of data-processing persons, records, and activities
• InstallShield, a software tool for creating software installers for Microsoft Windows
• IntelliStar, a computer system used to display local forecasts on The Weather Channel
• the relational operator is, used in Python
• the type comparison operator is, used in C#

• IS tank, a Soviet heavy tank in World War II.
• Istrebitel Sputnikov or "Destroyer of Satellites", a Soviet anti-satellite weapons program.
• Lexus IS, a sports car made by Lexus.
• Locomotive IS, a Soviet passenger steam locomotive.
• Nikitin-Shevchenko IS, a Soviet fighter aircraft.

• Image stabilization, a family of techniques to reduce blur caused by lens shakes
• Canon Image Stabilizer, a lens-based image stabilization technology by Canon
• Intrinsic safety, a protection technique for electronic equipment in explosive atmospheres
• Indian Standard, developed by the Bureau of Indian Standards, for example IS 456
• International Standard, a mounting standard for the calipers and rotors of disc-type bicycle brake systems

• Internal security, the work of keeping domestic peace by a national force
• International studies, or International relations, the study of politics, economics and law on a global level
• Is, in is-ought philosophy, a fact or empirical state with finite limits in space and time
• Old Israeli Shekel, commonly denominated as IS
• Islamic State, an Islamic terrorist organization

• I (disambiguation)
• Independence Square (disambiguation), several public squares around the world
• International System of Units (SI), the modern form of the metric system
• Interstate (disambiguation)
• Islamic state, a form of government based on Islamic law