Sif is a Norse goddess and the wife of Thor.

Sif or SIF may also refer to:

• Sif Atladóttir (born 1985), Icelandic footballer
• Sif Ríkharðsdóttir, Icelandic academic
• Sif Ruud (1916–2011), Icelandic actress
• Sif Rykær (born 1988), Danish footballer
• Sif Saga (born 1997), Icelandic model

• Sif (character), the Norse goddess as portrayed in Marvel Comics
  • Sif (Marvel Cinematic Universe), the character's portrayal in the MCU
• Sif (Dark Souls), a character in the video game Dark Souls

• Sif, Yemen
• Sif Glacier, Greenland
• Sif Island, Antarctica

• State Secretariat for International Finance, of the Government of Switzerland
• Society for Individual Freedom, a British association promoting individual freedom
• Somali Islamic Front, also known as Jabhatul Islamiya
• Strategic Innovation Fund, a program of the Government of Canada
• Syrian Islamic Front
• Statutes in Force, the 4th revised edition of the statutes in the United Kingdom

• Italian Physical Society (Italian: Società Italiana di Fisica)
• Safety instrumented function
• Schools Interoperability Framework, a data-sharing specification
• Selective Identification Feature, used to identify aircraft
• Small intensely fluorescent cell
• Source Input Format, a MPEG-1 video format
• Standard Interchange Format, a format for geographic data
• Stress intensity factor, used in fracture mechanics to predict the stress state

• Supreme Indoor Football, a defunct American sport league

• SÍF Sandavágur, a Faroese football club
• Sandvikens IF, a Swedish football club
• Silkeborg IF, a Danish football club
• Stattena IF, a Swedish football club in Helsingborg
• Stavanger IF, a Norgwegian football and handball club
  • SIF Stadion, their home venue
• Stocksunds IF, a Swedish sport club in Stocksund
• Strømsgodset IF, a Norwegian sport club
  • Strømsgodset Toppfotball, their professional football team

• AirSial, a Pakistani airline
• Rockingham County NC Shiloh Airport, in North Carolina
• Simara Airport, in Madhesh Province, Nepal
• TF-SIF (Dauphin 2), an aircraft operated by the Icelandic Coast Guard from 1985 until 2007
• TF-SIF (Dash 8), an aircraft operated by the Icelandic Coast Guard since 2009

• Central European Institute of Philosophy (Czech: Středoevropský Institut Filosofie)
• Science of Identity Foundation, an American religious organization
• Seychelles Islands Foundation
• Shropshire Islamic Foundation
• Singapore International Foundation, a Singaporean charity
• Swedish Union of Clerical and Technical Employees in Industry (Swedish: Sif)

• 4484 Sif, a main-belt asteroid
• Siamou language
• Sif Mons, a shield volcano on Venus
• Specialized investment fund
• Love Live! School Idol Festival, a mobile game

• Short Interframe Space (SIFS), the small time interval between the data frame and its acknowledgment