SFSR may refer to:

• A Soviet Federative Socialist Republic or Socialist Federative Soviet Republic, any of several Republics of the Soviet Union:
  • Russian Soviet Federative Socialist Republic (Russian SFSR) (1917–1991)
  • Transcaucasian Socialist Federative Soviet Republic (Transcaucasian SFSR) (1922–1936)
• Santa Fe Southern Railway, a short line railroad in New Mexico, United States
• San Francisco Syncope Rule, a clinical prediction rule for syncopal episodes