Health savings account

Home School Association, a common name for independent parent groups not associated with a formal Parent-Teacher Association

Homeland Security Advisory System

Human serum albumin

Hawker Siddelely Aviation

Stennis International Airport in Bay St. Louis, Mississippi has a FFA airport code of HSA (the ICAO code is KHSA)

The Book of Hosea has a common abbreviation of Hsa.

Humane Slaughter Act

High Speed Alliance, see HSL-Zuid

Hunt Saboteurs Association

Homeland Security Act

Hasimara railway station has a code of HSA

Human Security Act

Hmar Students Association

High School Assessments a Maryland Public School standardized test.

The Harlem School of the Arts

Haiku Society of America

Hispanic Student Association

Health Sciences Authority, a statutory board of the Ministry of Health of Singapore

Heat stable antigen, a cluster of differentiation, also known as CD24

Horizon Science Academy, a Columbus, OH based school.

Hoffman Sports Association, an organizing body for Freestyle BMX events worldwide

East African Safari Air has a ICAO Code of HSA

High Speed Amphibian vehicles from Gibbs, the maker of the Gibbs Aquada, Humdinga and Quadski