RSF was a French synthesizer manufacturer founded in the 1970s by brothers Ruben and Serge Fernandez, based in the Toulouse region of southwest France. The initials stand for the founders' names. The company began by building bespoke electronic modules for local musicians before introducing its Modular Series 11 in 1976, a large patch-cable system in the spirit of the ARP 2600.

RSF is best known for the Kobol, a monophonic analog synthesizer launched in 1978 that earned the nickname "the French Minimoog" for its rich, fat tone. The Kobol was unusual for its era in offering patch memory and a built-in step sequencer, and it was followed by the Kobol Expander rack modules in 1979. The brothers later expanded into polyphonic territory with the Polyclavier and the Polykobol, eventually releasing the more ambitious Polykobol II in the early 1980s. Production was always limited — fewer than 200 Kobol keyboards were built, and the Polykobol family was made in even smaller numbers.

The original company ceased trading in 1987, and surviving units have become highly collectible on the vintage market. Interest in the brand's designs has been kept alive by specialists and by reissues from other makers, including Behringer's Kobol Expander clone, developed with input from RSF historian Olivier Grall.

RSF has 5 products cataloged on Equipboard, including Synthesizers, Drum Machines, and Sound Modules. Their gear is featured by 4 artists, with the strongest followings in Electronic, Rock, and Pop. Notable users include Aphex Twin, Martin L. Gore, and Vince Clarke.