Sig used as a name may refer to:
- Sig (given name)
- Sig, Algeria, a city on the banks of the Sig River
- Sig Alert, an alert for traffic congestion in California, named after Loyd Sigmon
- Sig River, a river of Algeria also known as Mekerra
sig (lower case) may refer to:
- sig (rune), an Armanen rune, later used for the Schutzstaffel (SS) logo
- sig, the distinctive hand actions of sign language that form words; see movement (sign language)
- .sig, a signature block in e-mail messaging
sig as a loanword may refer to:
- sig (Russian), the common whitefish; see Coregonus
- Sig (Italian), abbreviation of Signore ("Lord")
- Sig. (Latin, also Signa or Signatura), the "signature" section of a medical prescription, which contains directions to the patient, and the signature of the prescribing doctor
- Sig. Signaling ( in Rail transport) the signals and associated equipment required for their operation.
SIG (capitalized) may refer to:
- SIG, the IATA Callsign of Fernando Luis Ribas Dominicci Airport in San Juan, Puerto Rico
- SIG (band), a Finnish band
- SIG Combibloc Group, a Swiss-German packaging company and former railway vehicle and firearms manufacturer
- SIG plc, a British insulation company, formerly Sheffield Insulations Group plc
- SIG Sauer, the brand name used by firearms manufacturers SIG Sauer Inc. of the United States and SIG Sauer GmbH of Germany
- S.I.G., the affirmative call sign (meaning "Spectrum Is Green") used by characters in the 1960s British TV series Captain Scarlet and the Mysterons
- the 15 cm sIG 33 (or Schweres Infanterie Geschütz) a German-made infantry gun used in World War II
- Susquehanna International Group, a privately held global trading and technology firm
SIG may also be used as an acronym to refer to:
- Särskilda Inhämtningsgruppen, a special forces unit of the Swedish Defence Forces, active 2007–2011
- Schweizerische Industrie Gesellschaft, the original name of SIG Combibloc Group
- Science Initiative Group, an international team of scientists dedicated to fostering science in developing countries
- Semen Indonesia Group, an Indonesian state-owned building materials manufacturer
- Shanghai International Group, state-owned financial services corporation
- Special Interest Group, a community with a common technical interest
- Examples include: Aviation SIG, Bluetooth SIG, Small Form Factor SIG
- Special Interrogation Group, the British Army unit of German-speaking Jewish volunteers in World War II
- Special Investigation Group, a New Zealand government group
- Strasbourg IG (Strasbourg Illkirch-Graffenstaden Basket), a French basketball club