Formal or informal associations of human beings, usually in pursuit of some common goal
- Oakland County, Libertarian Party of - Michigan
- Ohio, Libertarian Party of
- Okaloosa County, Libertarian Party of - Florida
- Oklahoma, Libertarian Party of
- Ontario, Freedom Party of - Canada
- Ontario Libertarian Party - Canada
- Orange County, Libertarian Party of - California
- Orange County, Libertarian Party of - Florida
- Oregon, Libertarian Party of