IAAS can refer to the following:
- Incorporated Association of Architects and Surveyors, British professional body renamed 1993 as the Association of Building Engineers
- Institute of Agriculture and Animal Science, institute of Tribhuvan University, Nepal
- International Association of Students in Agricultural and Related Sciences, Belgium-based international organisation
- International Association for Ambulatory Surgery, Belgium-based international organisation
- International Association for Astronomical Studies, Denver, Colorado based Student Astronomy Research Team
- Infrastructure as a service, concept in Cloud computing
- Irish Association of American Studies