LSI may refer to:
Science and technology
Large-scale integration, integrated circuits with tens of thousands of transistors Latent semantic indexing, a technique in natural language processing LSI-11, an early large-scale integration computer processor that implemented the DEC PDP-11 instruction set Langelier saturation index, a measure for water's tendency to form scale Linear shift-invariant systems, the discrete equivalent of linear time-invariant systems
Organizations
LSI Corporation, a technology company founded in 1981 as LSI Logic Corporation Lynch Syndrome International, non-profit organisation supporting those affected by Lynch Syndrome Labour and Socialist International, a multinational federation of left wing political parties and trade unions active between 1923 and 1940 Socialist Movement for Integration (Lëvizja Socialiste për Integrim), a political party in Albania Lear Siegler Incorporated, a technology company active from 1961 to 2002 Lingkaran Survei Indonesia, a survey company in Indonesia
Transportation
Lake Superior and Ishpeming Railroad, a railroad service in Michigan, United States Sumburgh Airport (IATA airport code) in Shetland, Scotland
Music
"LSI (Love Sex Intelligence)", a single by The Shamen Long-string instrument, a musical instrument
Other uses
Landing ship, infantry, a type of troopship or post World War II a landing craft La Salle Institute, a college preparatory school Linguistic Survey of India, a survey of the languages of British India directed by G.A. Grierson Logical Sensory Introvert, a socionics type Lighting & Sound International, a trade magazine