Isk or ISK may mean:
- Icelandic króna, the national currency of Iceland
- Internationaler Sozialistischer Kampfbund, a now-defunct German socialist party
- Iso suomen kielioppi
- the currency in the space MMORPG Eve Online
- half of any of the Iskoort, a fictional race of aliens from the Animorphs series
- ISK, also known as the notorious gang "Iwo Street Killas"