The Pompey stone was carved as a hoax near Pompey, New York, circa 1820. Upon its discovery that year, the stone was quickly accepted as authentic, dated to circa 1520, and extensively analyzed by historians of the day for its significance as an early record of European presence in the region. It was commonly thought to have marked the grave of a Spaniard, who was proposed to have been an explorer, missionary, or captive of a Native American tribe.

The hoax was generally accepted as authentic for the next seventy years, and after being displayed for a year in Manlius it was moved to Albany, first in the State Museum of the Albany Institute and after 1872 in the New York State Museum of Natural History. In 1894, the antiquarian William M. Beauchamp conducted research casting doubt upon the stone's age and suggesting it was a hoax. Later that year, the engineer John Edson Sweet publicly admitted that his relatives had carved the stone in the 19th century. The stone has since remained on display as an example of a hoax and as of 2018, was held by the Museum of the Pompey Historical Society.

The stone is roughly an oval, approximately 14 inches (360 mm) long, 12 inches (300 mm) wide, and 10 inches (250 mm) thick, and composed of gneiss. It weighs around 127 pounds (58 kg). The center of the stone is inscribed with a tree that is being climbed by a serpent. The stone was initially engraved with "Leo De L on VI 1520", which was translated in 1841 by the historians John Warner Barber and Henry Howe as meaning "Leo X by the Grace of God; eighth year of his pontificate, 1520".

In 1937, Noah T. Clarke, the New York state archaeologist, noted that the stone's inscription had been changed, with the 1520 altered to read 1584, and the 'L on' disappeared. He attempted to restore other parts of the stone, but was limited in research as many records had been destroyed in the 1911 New York State Capitol fire.

According to an 1894 letter published in the Syracuse Journal by John Edson Sweet, Sweet's uncle Cyrus Avery and Avery's nephew, William Willard, carved the stone and buried it in a field in Pompey "just to see what would come of it". The two decided not to come forward after it started to attract scholarly attention.

The stone was discovered by Philo Cleveland, a farmer living near Watervale, New York. In the summer of 1820 he began efforts to expand a patch of meadow on his farm. He was well into clearing the land, cutting down trees and removing stones, when he dug up the Pompey stone. Cleveland reportedly did not notice it and had stopped to take a break when he saw the inscription. He did not pay it much attention until several days later, at which point rain had cleaned the stone.

Intrigued by the stone, Cleveland brought it to the local blacksmiths. The stone became a local attraction and visitors to the shop used nails and files to dig out the inscription; Huguenin attributes this to giving the stone "somewhat the appearance of a new work." After about six months in Watervale, it was moved to the nearby village of Manlius, and while there was visited by several scientists. The stone was then put on display in the State Museum of the Albany Institute, after about a year in Manlius. In 1872, the Albany Institute deposited the stone with the New York State Museum of Natural History, which the State Museum described in their Annual Report as being intended to provide "better facilities for the inspection" of the stone. By 1880 the stone was on display in the New York State Museum of Natural History.

The stone began receiving published analysis as early as 1823, when an article republished in The Literary Chronicle analyzed the stone's inscription; concluding that it could be a reference to Pope Leo X's reign, the drawing in the middle a tree and serpent representing the fall of man, the letters L. s. as standing for loco sigilli (the place of a seal), a cross emphasizing the stone's Christian connections, and inverted U as marking the location of a seal.