FSN may refer to:

• Fate/stay night, a visual novel and its adaptations.
• The Federal Stock Number, a numeric code used to identify items in the Joint Army-Navy Catalog System.
• The Federation of Student Nationalists: the student wing of the Scottish National Party.
• Filter Smoke Number
• Five-seveN, a semi-automatic pistol designed and manufactured by FN Herstal in Belgium.
• Forest Star Networks, a Telecom Operator Enabler within the VoIP and Fixed & Mobile VNO and Metro Networks segment.
• Fox Sports Net, a national network of regional sports channels in the United States
• Fox Sports News, an Australian cable and satellite sports news channel.
• Full Service Network, a Pittsburgh based competitive local exchange carrier
• Full Service Network, a defunct digital video broadcasting service
• FSN Broadband, an Internet and Broadband Phone Service Provider
• Global Forum on Food Security and Nutrition
• Fronte Sociale Nazionale (National Social Front), an Italian far right political party
• Frontul Salvarii Nationale (National Salvation Front), a former revolutionary group and governing political party of Romania
• Fsn, a 3-D file manager that appeared in the movie Jurassic Park

fsn (File System Navigator) pronounced as "fusion" is an experimental application to view a file system in 3D, made by SGI for IRIX systems.

FSN steht als Abkürzung für:

• Schweizerischer Schwimmverband
• Frontul Salvarii Nationale, rumänische Nationale Befreiungsfront
• Fox Sports Net, Sportsender im US-Fernsehen

FOXスポーツネット(Fox Sports Net FSN)は米FOXテレビにおけるスポーツ専門チャンネル。

Frontul Salvării Naţionale (FSN) a fost o formaţiune politică postcomunistă, înregistrată în registrul partidelor politice în 6 februarie 1990, urmare a transformării Consiliului Frontului Salvării Naţionale, organ provizoriu al puterii de stat rezultat după revoluţia română din 1989, în partid politic.