FSL

The abbreviation FSL may refer to:

• Florida State League
• FMRIB Software Library
• Freescale Semiconductor stock symbol
• Free-space path loss or free-space loss (FSL) in telecommunications
• Finnish Sign Language
• French Sign Language
• French as a second language
• Friends' School, Lisburn, a grammar school in Lisburn, Northern Ireland
• Fleet Support Limited
• Fast Simplex Link, an interface by Xilinx used in the MicroBlaze soft processor
• Fluid Science Laboratory