FSK may refer to:

• FSK (band), a German band
• Federal Counterintelligence Service, (Russian Федера́льная Слу́жба Контрразве́дки; Federalnaya Sluzhba Kontrrazvedki) of Russia
• Fiskerton railway station, in England
• Forskolin, a diterpene
• Forsvarets Spesialkommando, a Norwegian special forces unit
• Fort Scott Municipal Airport, in Kansas, United States
• Francis Scott Key Bridge (disambiguation)
• Francis Scott Key High School, in Union Bridge, Maryland, United States
• Freiwillige Selbstkontrolle der Filmwirtschaft, a German movie rating organization
• Frequency-shift keying
• Friends School Kamusinga, in Kenya
• Kosovo Security Force, (Albanian: Forca e Sigurisë së Kosovës)