YSA may refer to:
- Young Scientists of Australia, an organization dedicated to the promotion of science in Australia to the 15- to 25-year-old demographic
- Young Single Adult, a designation in The Church of Jesus Christ of Latter-day Saints (LDS Church) for unmarried people between the ages of 18 and 30
- Youth Service America, a U.S. organization promoting increased opportunities for youth voice and service learning.
- Young Socialist Alliance youth organization of the US Socialist Workers Party