FSB (Bulgarian: ФСБ) (abbreviation for Formation Studio Balkanton) are a Bulgarian progressive rock band formed in 1975 in Sofia as a studio project. FSB achieved great success in the 1980s and performed in numerous countries across Europe. Their collaboration with singer Jose Feliciano resulted in the album I'm Never Gonna Change and a Grammy award in 1990.

• Rumen Boyadzhiev — vocals, keyboards (1975–present)
• Konstantin Tsekov — keyboards, vocals (1975–present)
• Ivan Lechev — guitar (1979–present)

• Aleksandar Baharov — bass (1975–1983)
• Peter Slavov — drums (1979–2006, d.2008)
• Ivaylo Kraychovski — bass (1983–2007, d.2018)

• Official website
• (in Bulgarian) FSB at Bulgarian Rock Archives