SIAC is an acronym used by several bodies:
- Securities Industry Automation Corporation
- Singapore International Arbitration Centre
- Sistema Integrado de Artilleria de Campaña, General Dynamics Santa Bárbara Sistemas
- La Sociedad Interamericana de Astronomía en la Cultura
- Southern Indiana Athletic Conference, a high school athletic conference
- Southern Intercollegiate Athletic Conference, an NCAA Division II collegiate athletic conference
- Special Immigration Appeals Commission
- State Institute for Administrative Career, one of the six colleges at the Government Colleges Hostel, Mumbai