Thomas Paine (February 9, 1737 – June 8, 1809) was an English-born American political activist, philosopher, political theorist, and revolutionary. He authored Common Sense (1776) and The American Crisis (1776–1783), two of the most influential pamphlets at the start of the American Revolution, and helped inspire the Patriots in 1776 to declare independence from Great Britain, hitherto an unpopular cause. His ideas reflected Enlightenment-era ideals of transnational human rights.

Born in Thetford, Norfolk, Paine emigrated to the British American colonies in 1774 with the help of Benjamin Franklin, arriving just in time to participate in the American Revolution. Virtually every rebel read (or listened to a reading of) his 47-page pamphlet Common Sense, proportionally the all-time best-selling American title, which catalysed the rebellious demand for independence from Great Britain. The American Crisis was a pro-revolutionary pamphlet series.

Paine lived in France for most of the 1790s, becoming deeply involved in the French Revolution. While in England, he wrote Rights of Man (1791), in part a defense of the French Revolution against its critics. His attacks on Anglo-Irish conservative writer Edmund Burke led to a trial and conviction in absentia in England in 1792 for the crime of seditious libel.

The British government of William Pitt the Younger, worried by the possibility that the French Revolution might spread to Britain, had begun suppressing works that espoused radical philosophies. Paine's work, which advocated the right of the people to overthrow their government, was duly targeted, with a writ for his arrest issued in early 1792. Paine fled to France in September where, despite not being able to speak French, he was quickly elected to the French National Convention. The Girondins regarded him as an ally; consequently, the Montagnards, especially Maximilien Robespierre, regarded him as an enemy.

In December 1793, he was arrested and was taken to Luxembourg Prison in Paris. While in prison, he continued to work on The Age of Reason (1793–1794). James Monroe, a future President of the United States, used his diplomatic connections to get Paine released in November 1794. Paine became notorious because of his pamphlets and attacks on his former allies, who he felt had betrayed him. In The Age of Reason and other writings he advocated Deism, promoted reason and freethought, and argued against institutionalized religions in general and the Christian doctrine in particular. In 1796, he published a bitter open letter to George Washington, whom he denounced as an incompetent general and a hypocrite. He published the pamphlet Agrarian Justice (1797), discussing the origins of property and introduced the concept of a guaranteed minimum income through a one-time inheritance tax on landowners. In 1802, he returned to the U.S. When he died on June 8, 1809, only six people attended his funeral, as he had been ostracized for his ridicule of Christianity and attacks on the nation's leaders.