The noun is derived from liberty + -arian.

The word was first attested in English in 1789 in William Belsham’s Essays: see the quotation. This was contrasted with necessitarian, in the context of free will, and was not used in the more frequently encountered modern sense.

Compare French libertaire, from liberté + -aire.

Sense 3.2 (“believer in right-libertarianism”) developed in the United States in the 1940s and was popularized in the 1950s. In the 1940s, Leonard Read (1898–1983), the founder of the Foundation for Economic Education, a free-market think tank, began calling himself “libertarian” in contrast with a “classical liberal”. In 1955, Dean Russell also promoted the use of the word, writing: “Let those of us who love liberty trade-mark and reserve for our own use the good and honorable word ‘libertarian’.”

• (RP) IPA: /ˌlɪb.əˈtɛə.ɹɪ.ən/, /-ɹj-/
• (America) IPA: /ˌlɪb.əɹˈtɛ.ɹi.ən/
• (Australia) IPA: /ˌlɪb.ɪˈteː.ɹɪ.ən/, /-ɹj-/

libertarian (plural libertarians)

1. One who advocates liberty, either generally or in relation to a specific issue.

   Synonyms: eleutheromaniac

   Antonyms: antilibertarian, nonlibertarian

   Hyponym: anarchist

   civil libertarian

   cultural libertarian

2. (philosophy) A believer in the freedom of thinking beings to choose their own destiny (the doctrine of free will) as opposed to those who believe the future is predetermined (the doctrine of necessity). [from late 18th c.]

3. (politics) One who advocates libertarianism; also, a member of a political party supporting libertarianism.

   Antonyms: antilibertarian, nonlibertarian

   1. (chiefly, Ireland, UK) An antiauthoritarian believer in left-libertarianism, a political doctrine that stresses both individual freedom and social equality, and advocates shared ownership of natural resources.
   2. (chiefly, US) A believer in right-libertarianism, a political doctrine that emphasizes individual liberty and a lack of governmental intervention, oversight, and regulation, both in economic matters (that is, a belief in the free market) and in personal behaviour provided that no one's rights are threatened or violated.

• French: libertaire
• Italian: libertario, libertaria
• Portuguese: libertário, libertária
• Spanish: libertario, libertaria

libertarian

1. Advocating liberty; also, having a relative tendency towards liberty.

   Antonyms: antilibertarian, nonlibertarian

   He has libertarian views.

2. (philosophy) Relating to the doctrine of free will as opposed to the doctrine of necessity.

   Antonyms: necessitarian

3. (originally, US, politics) Relating to, or advocating, libertarianism; also, relating to a political party supporting libertarianism.

   Antonyms: antilibertarian, nonlibertarian

   a libertarian capitalist

   • 2016 January 13, Ben Jacobs, “Ron Paul criticizes Cruz’s absence from Fed vote in support of son’s campaign”, in Katharine Viner, editor, The Guardian‎^{[https://web.archive.org/web/20230427072659/http://www.theguardian.com/us-news/2016/jan/13/ron-paul-rand-paul-ted-cruz-federal-reserve-vote]}, London: Guardian News & Media, →ISSN ↗, →OCLC ↗, archived from the original ↗ on 2023-04-27:

     Rand Paul's presidential campaign has drafted in his father, libertarian icon Ron Paul, to directly attack Republican rival Ted Cruz in a robocall in Iowa, the first time the former presidential candidate has gone on the offensive on his son’s behalf.

• French: libertaire

libertarian (plural libertarians)

1. (politics) A member of a political party or movement that uses the term "Libertarian" in its name (e.g., the Libertarian Party of the United States); one who is likely to support policies that are libertarian.

libertarian (not comparable)

1. (politics) Of, or pertaining to, a Libertarian Party.

• French: libertarien