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