Lysander Spooner (January 19, 1808 – May 14, 1887) was an American individualist anarchist. He was also an abolitionist, entrepreneur, essayist, legal theorist, pamphletist, political philosopher, Unitarian, writer and a member of the First International.
Spooner was a strong advocate of the labor movement and anti-authoritarian and individualist anarchist in his political views. His economic and political ideology has usually been identified as libertarian socialism and mutualism. His writings contributed to the development of both left-libertarian and right-libertarian political theory within libertarianism in the United States.
Spooner's writings include the abolitionist book The Unconstitutionality of Slavery and No Treason: The Constitution of No Authority, which opposed treason charges against secessionists. Spooner is also known for competing with the Post Office with his American Letter Mail Company. However, it was closed after legal problems with the federal government.