IK or Ik may mean:
- IK Investment Partners, a European private equity firm
- Inupiaq language (ISO 639 alpha-2), a group of dialects of the Inuit language, spoken in northern and northwestern Alaska.
- Ik people of Uganda, made famous by anthropologist Coin Turnbull's book The Mountain People
- The Ik language
- Ik River in Russia
- IK code, a classification of resistance to mechanical impacts
- an abbreviation for Inverse kinematics, a branch of mechanics
- an acronym for Index Kewensis, a publication maintained by the Royal Botanic Gardens, Kew
- an abbreviation for Iparretarrak, the Basque nationalist organization
- the IATA airline designator of Imair Airlines
- the regional code for Ilm-Kreis in Germany
- an abbreviation for the German term Internationale Kerze (international candle), an old photometric unit to measure luminous intensity
- a Dutch word for "I" (the first-person singular personal pronoun in the subject case)
- an abbreviation for the computer game International Karate
- an acronym for "I know", used in instant messaging and chat rooms
- Indigenous knowledge, another name for traditional knowledge such as that held by indigenous peoples