Organizations
- Haiku Society of America
- Harvard Student Agencies, world's largest student-run corporation
- Hawker Siddeley Aviation
- Hispanic Student Association, a type of student organization
- Hmar Students Association
- Hoffman Sports Association, an organizing body for Freestyle BMX events worldwide
- Hunt Saboteurs Association, an animal rights organization
- High Speed Alliance, a Dutch high-speed rail company
Read more about this topic: HSA