agreement negotiated in 1901 between the U.S. and Great Britain, providing for the construction and regulation of a canal across the Isthmus of Panama; it was signed by John Hay, U.S. secretary of state, and Lord Julian Pauncefote (1828–1902), British ambassador to the U.S. The treaty superseded the Clayton-Bulwer Treaty of 1850 as the definitive statement of Anglo-American policy concerning an Atlantic-Pacific canal.

The Spanish-American War of 1898 created an American interest in South and Central America. American public opinion began to demand abrogation of the 1850 treaty, which permitted neither the U.S. nor Great Britain to act alone in regard to the canal. The French engineer Ferdinand de Lesseps had tried unsuccessfully to dig an isthmian canal in the 1880s, but the U.S., in 1900, decided that such an enterprise should be entirely American. Great Britain was amenable, provided that the canal zone would remain neutral.

Conversations between Hay and Pauncefote resulted in a draft treaty giving the U.S. complete direction of the construction project, establishing permanent neutrality of the zone and a ban on fortifications, and inviting other nations to join in guarantees of neutrality. The U.S. Senate, refusing to ratify the original draft, amended it to permit the U.S. to take any measures for its own defense in the canal zone and deleted the clause concerning other nations. Great Britain opposed these amendments, and negotiations were resumed. A revised draft was presented to the Senate in 1901 and was ratified shortly after its presentation. By the terms of the ratified treaty, the U.S. was given full control of the construction and management of the canal; the U.S. was named sole guarantor of the neutrality of the canal and was permitted to build fortifications; and the canal was opened to ships of any nation under equal terms, although the U.S. could forbid passage in times of war. In 1911 Great Britain claimed that the U.S. had contravened the last clause by passing the Panama Canal Act, exempting American coastal shipping from paying canal tolls; President Woodrow Wilson, agreeing with the British view, persuaded Congress to repeal the act in 1914.

See also PANAMA CANAL,.