IIS is an acronym that may stand for:
- Internet Information Services, a set of Internet-based services for servers using Microsoft Windows
- I²S or Inter-IC Sound, a serial bus for audio transmissions
- Indian Institute of Science in Bangalore, India
- Iraqi Intelligence Service, also known as the Mukhabarat
- Institute of Ismaili Studies, London in the United Kingdom
- International Indian School, Dammam, located in Dammam, Saudi Arabia
- Indian Information Service, A professional service of the Government of India for journalists
- Institute of Information Scientists, which merged with the Library Association to form Chartered Institute of Library and Information Professionals
- IIS, IATA airport code of Nissan Island Airport in Papua New Guinea