Arthur Lee (20 December 1740 – 12 December 1792) was an American physician, diplomat and abolitionist who was born in the British colony of Virginia. He helped negotiate and signed the 1778 Treaty of Alliance with France, along with Benjamin Franklin and Silas Deane, which allied France and the United States in fighting the war.

Lee was educated in medicine and law at the University of Edinburgh and in London, respectively. After passing the bar, he practiced law in London for several years. He stayed in London during the Revolutionary War, representing the colonies to Britain and France and also serving as an American spy to track their activities. After his return to Virginia, he served as a delegate to the Continental Congress.

Born at Stratford Hall, Virginia, Arthur Lee was the youngest son of Hon. Thomas Lee (1690–1750), of the Lee Family of Virginia, and Hannah Harrison Ludwell (1701–1750). Three of his five surviving elder brothers, Richard Henry Lee (1732–1794), Francis Lightfoot Lee (1734–1797) and William Lee (1739–1795), also became Revolutionary-era diplomats.

He attended Eton College in England and studied medicine at the University of Edinburgh, where he graduated in 1764. The title description of his thesis is: Dissertatio medica inauguralis, de cortice peruviano: quam ... ex auctoritate ... Gulielmi Robertson ... Academiae Edinburgenae praefecti ... pro gradu doctoratus ... eruditorum examini subjicit, Arthur Lee, Virginiensis. Ad diem septembris [1764] ... – Edinburgi : in aedibus A. Donaldson et J. Reid, MDCCLXIV. – 2 p. l., 47 p. ; 20 cm. on 13 May 1765 he matriculated at the University of Leiden in the Netherlands.

During the latter period, Lee wrote in 1764, "An Essay in Vindication of the Continental Colonies of America," one of his more noted works. He opposed the Townshend Acts and became a major proponent of the Patriot cause. After this work, he was granted membership to the American Philosophical Society through his election in 1768.

He studied law in London, passing the bar, and practising there from 1770 to 1776. During this time in London, Lee wrote many influential pamphlets and essays opposing slavery and Parliament's policies. He lived at Poland Street with Paul Wentworth (counsellor) for five years.

In 1770, Lee in London was named as the Massachusetts correspondent to Britain and France. He began corresponding with Samuel Adams, which began a long friendship. They probably did not meet personally until sometime after 1780. Lee met Benjamin Franklin while he was in London, where Franklin was negotiating on behalf of Pennsylvania interests. Lee criticized Franklin's extravagant lifestyle and told Sam Adams he would never be a good negotiator between a free people and a tyrant.

In May 1776, he was a guest at the dinner organized by publisher Charles Dilly that—at the urging of James Boswell—brought together Samuel Johnson, an ardent opponent of the Patriot cause, and John Wilkes, one of its most prominent British supporters.