L1

L1, L01, L.1, L 1 or L-1 may be:
* L1 A1, a British self load rifle
* L₁ distance in mathematics
* L¹, the space of Lebesgue integrable functions in mathematics
* L1 family, a protein family of cell adhesion molecules
* L-1 Identity Solutions, Inc, a US face-recognition corporation
* L1 Portable Line Array - Bose Corporation
* L1 (protein), a cell adhesion molecule
* L-1 visa, a document used to enter the United States for the purpose of work

; containing L1 :
* Arado L 1, a 1929 German two-seat parasol-wing sporting monoplane
* ATC code L01, a section of the Anatomical Therapeutic Chemical Classification System
* DSC-L1, a 2004 Sony Cyber-shot L series camera model
* Erie L-1, a 1907 American 0-8-8-0 steam locomotive model
* Haplogroup L1 (mtDNA)
* Lawrance L-1, a predessecor of the 1920s American Lawrance J-1 aircraft engine
* Luxo L-1, a famous lamp
* Macchi L.1, a 1915 Austrio-Hungarian reconnaissance flying boat
* NCC Class L1, a Northern Counties Committee Irish steam locomotive model
* Panasonic Lumix DMC-L1, a 2006 single-lens reflex camera
* SP&S Class L-1, a 1891 steam locomotives class
* USS L-1 (SS-40), a 1915 United States Navy L-class submarine

and also :
* the Level-1 CPU cache in a computer
* Lufthansa Systems IATA code
* a person's first language
* Ligue 1, the top division of French football
* L=1, Lunar Eclipse classification on the Danjon scale
* a designation for the Stinson Model 74 Vigilant observation aircraft
* the first Lagrange Point in an astronomical Solar System
* the first lumbar vertebra of the vertebral column, in human anatomy
* a class of FM broadcast station in North America