Formal or informal associations of human beings, usually in pursuit of some common goal
- Acton Institute - Promotes a free and virtuous society characterized by individual liberty
- Advocates for Self-Government - Non-profit, non-partisan libertarian educational organization
- Association of Libertarian Feminists - Libertarian alternative to aspects of women's movement that discourage independence and individuality
- Atlas Network - Helps to develop a network of worldwide market-oriented think tanks
- American Enterprise Institute - Dedicated to preserving and strengthening the foundations of freedom
- Adam Smith Institute, The - Innovator of market economic policies in the U.K.
- Alabama, Libertarian Party of
- Alaska Libertarian Party
- Allegheny County, Libertarian Party of - Pennsylvania
- Antelope Valley Libertarian Party - California
- Arizona Libertarian Party, Inc.
- Arkansas Libertarian Party
- Atlas para una Sociedad Libre, Fundación - Buenos Aires, Argentina