SF may be:

• San Francisco, California
• Speculative fiction
• Science fiction
• the abbreviation for Scuderia Ferrari is displayed in the company's prancing horse coat of arms
• the retired US Navy hull classification symbol for Fleet Submarine
• SourceForge
• Street Fighter
• Super Fitness (the logo also used these two letters)
• Special Forces.
• Socialistisk folkeparti (Socialist People's Party) (Denmark)
• Suomi Finland (not used anymore)
• Short for Special Force's CPU, a rare implant in the MMORPG Neocron