Isl (or isl) is a common abbreviation for "island" or "islands".
ISL may also refer to:
- Iceland, a Nordic European island country.
- Independent Socialist League, a defunct Trotskyist group in the United States (originally called the "Workers Party").
- In-situ leach, a mining technique.
- Intercon Security, a security firm.
- International Socialist Left (Germany) (German: internationale sozialistische linke), a Trotskyist group in Germany.
- International Sport and Leisure, a bankrupt Swiss sports marketing company that was closely affiliated with FIFA and the IOC.
- Irish Shipping Limited, an Irish state-owned deepsea shipping company formed during World War II.
- Cisco Inter-Switch Link, a proprietary Cisco VLAN trunking protocol.
- Lyapunov stability in mathematics, from the phrase "n the ense of yapunov".
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