Crime scene investigator

CSI: Crime Scene Investigation, a popular television show about forensic scientists

CSI: Miami, a spin-off show of the above

CSI: NY, another spin-off of the above

Church of Scientology International, the largest organization devoted to the practice and the promotion of the Scientology belief system

CompuServe Inc., the first major commercial online service in the United States

Committee for Skeptical Inquiry, the organization formerly known as CSICOP

CSI franchise

College of Staten Island, one of the "hybrid colleges" of the City University of New York

Church of South India, a union of protestant Christian churches spread over South India

Control Sequence Introducer, a control character for initiating escape sequences

Companion in The Most Exalted Order of the Star of India

CSI: 3 Dimensions of Murder, the third game in the series

Container Security Initiative

CSI is a three-letter abbreviation that may stand for:

Civilian Saucer Investigations of Los Angeles

CSI: Hard Evidence the fourth in the series, released in fall 2007.

CSI: Crime Scene Investigation (computer game), a spin-off game

CSI: Miami (computer game), a spin off game

CSI (comic book), comic tie-in to the various series

CSI: Dark Motives, a spin-off game

Chlorosulfonyl isocyanate, a reagent in organic synthesis

Computer Society of India

Computer Security Institute, a computer organization

Carbon/Silicon, a british rock band.

Civilian Saucer Intelligence of New York City

Christian Surfers International, an evangelical mission agency which seeks to convert surfers to Christianity through the sport of surfing

CSI (novels), novelizations of the series

Construction Specifications Institute

Crimestoppers International Foundation

Crime Stoppers International and

Caesium iodide or cesium iodide (strictly CsI), an ionic compound used in chemistry

Canadian Securities Institute, the educational body of the Investment Dealers Associations of Canada

California Solar Initiative

Cite Scolaire Internationale de Lyon, an international highschool in Lyon, France

CSI (video games), a number of video games including:

Counter-scanned images

Christian Schools International, an organization that supports Christian school teachers who want Bible-based textbooks for their classrooms

Commission Sportive Internationale, a former part of Fédération Internationale de l'Automobile (FIA) that ruled motorsport, later known as FISA

Centre de Sociologie de l'Innovation, a research center in France

Consorzio Suonatori Indipendenti an Italian band evolved from former punk/art band CCCP Fedeli alla linea.

College of Southern Idaho, a community college in Twin Falls, Idaho

Common System Interface or Intel QuickPath Interconnect, a future computer bus being planned by Intel

Catalog Search Interface, a component of the IBM MVS operating system

Catholic Scouts of Ireland, one of the scouting organisations which joined to from Scouting Ireland in 2004.

CSI is the ICAO airline designator for Central Skyport, United States