| Acronym | Definition |
|---|
| FSL | Florida State League |
| FSL | French as a Second Language |
| FSL | Forensic Science Laboratory (various organizations) |
| FSL | Firstsource Solutions Ltd. (various locations) |
| FSL | Food Security and Livelihood (hunger prevention) |
| FSL | Finlands Svenska Lärarförbund (Swedish: Finnish Swedish Teachers; union) |
| FSL | Fonds de Solidarité Logement (French: Housing Solidarity Fund) |
| FSL | Fast Simplex Link |
| FSL | Foundstone Scripting Language |
| FSL | Forecast Systems Laboratory (NOAA) |
| FSL | Federal, State, Local |
| FSL | Fluid Science Laboratory |
| FSL | Fidelity Security Life (insurance; Kansas City, MO) |
| FSL | Foundation for Senior Living (Phoenix, AZ) |
| FSL | Full Supply Level |
| FSL | Free Space Loss (propagation loss) |
| FSL | Fast Simplex Link (uni-directional point-to-point communication channel bus) |
| FSL | Food Safety Laboratory (various locations) |
| FSL | FMRIB Software Library |
| FSL | Fiscal Services Limited (Jamaica) |
| FSL | French As Second Language |
| FSL | Fleet Support Limited (Portsmouth, UK) |
| FSL | Fire Services Levy (insurance, Australia) |
| FSL | Full Service Leasing |
| FSL | Flight Simulation Laboratory (various organizations) |
| FSL | Finite State Language |
| FSL | Furniture Symbol Library (space planning software) |
| FSL | Foundstone Scripting Language (programming) |
| FSL | First Sea Lord (British Navy) |
| FSL | Full Stop Landing |
| FSL | Foreign Secretary Level (international talks) |
| FSL | Flight System Laboratory |
| FSL | Framework Standard Library (software) |
| FSL | Forward Stocking Location |
| FSL | Field Stocking Location |
| FSL | Full Service Level (FAA) |
| FSL | Fragg Show Lübeck (gaming clan) |
| FSL | Financial Services Licensee |
| FSL | Frame Sync Length |
| FSL | Forms Source Language |
| FSL | Financial Services Lab |
| FSL | Forward Supply Location |
| FSL | Funded Staffing Level |
| FSL | Ferrite Single Line |
| FSL | Five Star Logistics Ltd. (Comet Shipping Agencies Nigeria Ltd.) |
| FSL | Flip Side Legends |
| FSL | Future Sustainability Leadership (Australia) |
| FSL | Frank-Starling Law |
| FSL | Forward Staging Location |