Isl (or isl) is a common abbreviation for "island" or "islands".

ISL may also refer to:

Education and research

• Illinois Security Lab, a research laboratory at the University of Illinois at Urbana-Champaign
• Independent School League (disambiguation), independent high school athletic conferences in the United States
• Institute of State and Law, a Russian legal think tank affiliated with the Russian Academy of Sciences
• International School of Louisiana, a charter school system in the United States
• International School of Lusaka, an international school in Zambia
• International School of Luxembourg, a privately owned non-profit school in Luxembourg
• International School of Lyon, an international school in France

Languages

• Icelandic language (ISO 639-2 tag: ISL), a language spoken in Iceland
• Icelandic Sign Language, the sign language of Iceland
• Indian Sign Language also known as sign language of the deaf community in India
• International Sign Language, any of several international auxiliary languages
• Irish Sign Language, the sign language of Ireland
• Israeli Sign Language, the most commonly used sign language within Israel's deaf community
• Italian Sign Language, sign language used for Italian deaf people

Sports

• Independent School League (Illinois), a group of nine Chicago-area preparatory schools
• Independent School League (New England), a group of 16 New England preparatory schools
• Independent School League (Washington, D.C. area), a group of 17 Washington, D.C. preparatory schools
• Interscholastic League of Honolulu, a group of Hawaiian private schools
• Indian Super League, a professional football-club league based in India
• Ice Hockey Superleague, a British-based ice hockey league that existed between 1996 and 2003
• Indonesia Super League, the top-tier competition for football clubs in Indonesia
• International Soccer League, a U.S. based soccer league which was formed in 1960 and collapsed in 1965
• International Sport and Leisure, a bankrupt Swiss sports marketing company that was closely affiliated with FIFA and the IOC
• Iranian Super League (disambiguation), the Iranian professional basketball, futsal or volleyball leagues
• Island Soccer League, a professional six-a-side association football league based in Bermuda
• International Swimming League, a professional swimming league with ten teams and nine rounds in different cities all over the world

Transport

• Island line (MTR), one of the rapid transit railway lines in Hong Kong
• Isleworth railway station, London, England (National Rail station code)
• Atatürk Airport, a former major international airport serving Istanbul, Turkey now serves cargo flights

Political organizations

• Independent Socialist League, a defunct Trotskyist group in the United States (originally called the "Workers Party")
• International Socialist League (South Africa), a former syndicalist group
• International Socialist League (UK), a Trotskyist party in United Kingdom
• International Socialist League (2019), an international Trotskyist organization
• International Socialist Left (Germany) (German: internationale sozialistische linke), a Trotskyist group in Germany

Other uses

• Iceland, a Nordic European island country
• In situ leach, a mining technique
• Independent state legislature theory, U.S. Constitution reading
• Integer set library (isl), a programming library for manipulating integer sets
• Inter-Switch Link (disambiguation), a specially configured connection between network equipment
  • Cisco Inter-Switch Link, a proprietary Cisco VLAN trunking protocol
• Intercon Security, a security firm
• Irish Shipping Limited, an Irish state-owned deepsea shipping company formed during World War II
• i. s. L., "in the sense of Lyapunov" (in mathematical contexts), a reference to Lyapunov stability
• International Service Learning, a humanitarian NGO that offers volunteers practical experience in medical, education, and community enrichment programs