| Acronym | Meaning |
| LIT | Linear Ion Trap |
| LITA | Laser-induced Thermal Acoustics |
| LITD | Lased Induced Thermal Desorption |
| LITGS | Laser Induced Thermal Grating Spectroscopy |
| LITJ | Laser-Induced Temperature Jump |
| LIVA | Light-induced Voltage Alteration |
| LKKR | Layer Korringa-Kohn-Rostoker (in Interface Electronic Structures) |
| LLC | Lewis Lung Carcinoma |
| LLC | Lyotropic Liquid Crystal |
| LLD | Lower Limit Of Detection |
| LLDPE | Linear Low Density Polyethylene |
| LLE | Liquid Liquid Extraction |
| LLIT | Liq.-liq. Intermol. Transfer |
| LLME | Liquid-liquid Micro Extraction |
| LLNL | Lawrence Livermore National Laboratory |
| LLOD | Lower Limit Of Detection |
| LLOQ | Lower Limit Of Quantitation |
| LLRD | Long-lived Radioactive Dust |
| LLRW | Low Level Radioactive Waste |
| LLS | Laser Light Scattering |
| LLS | Linear-least Squares |
| LLT | Laser Luminescence Tomography |
| LLW | Low-Level Waste |
| LMC | Large Magellanic Cloud |
| LMC | Laminated Metal Composite |
| LMC | Low-pressure Molding Compound |
| LMCT | Ligand-to-metal Charge Transfer |
| LMDPE | Linear Medium Density Polyethylene |
| LME | Liquid-metal Embrittlement |
| LMF | Ladle Metallurgical Facility |
| LMFBR | Liquid-Metal Fast Breeder Reactor |
| LMHEMT | Lattice Matched High Electron Mobility Transistor |
| LMIS | Liquid Metal Ion Source |
| LMMS | Laser-microprobe Mass Spectrometry |
| LMO | Localized Molecular Orbital |
| LMO | Localized Molecular Spin Orbital |
| LMOS | Lake Michigan Ozone Study |
| LMP | Laser Microprobe |
| LMR | Laser Magnetic Resonance |
| LMR | Liquid Metal Reactor |
| LMREE | Light-medium Rare Earth Element(s) |
| LMSA | Linear Multivariate Statistical Analysis |
| LMSAL | Lockheed Martin Solar And Astrophysics Laboratory |
| LMT | Liquid Membrane Transport |
| LMTD | Logarithmic Mean Temperature Difference |
| LMTO | Linear Muffin-tin Orbital |
| LMW | Low Molecular Weight |
| LMWH | Low-molecular-weight Heparin |
| LMXB | Low-mass X-ray Binaries |
| LNA | Locked Nucleic Acid |