Hailes Abbey is two miles northeast of Winchcombe, Gloucestershire, England. The abbey was founded in 1245/6 by Richard, Earl of Cornwall, called "King of the Romans" and the younger brother of King Henry III of England. He was granted the manor of Hailes by Henry, and settled it with Cistercian monks from Beaulieu Abbey in Hampshire. In the previous generation, the manor had been the bithplace of an important theologian, Alexander of Hales, who had recently died in Paris. The great Cistercian abbey was entirely built in a single campaign and was consecrated in a royal ceremony that included the King and Queen and 15 bishops. Hailes Abbey became a site of pilgrimage when Richard's son Edmund donated to the Cistercian community a phial of the Holy Blood, purchased in Germany, in 1270.

A relic of the Crucifixion was a considerable magnet for pilgrimages. From the proceeds, the monks of Hailes were able to rebuild the Abbey on a magnificent scale

Though King Henry VIII's commissioners declared the famous relic to be nothing but the blood of a duck, regularly renewed, and though the Abbot Stephen Sagar admitted that the Holy Blood was a fake, in hope of saving the Abbey, Hailes Abbey was one of the last religious institutions to acquiesce following the Dissolution Act of 1536. The Abbot and his monks finally surrendered their abbey to Henry's commissioners on Christmas Eve 1539. Tewkesbury Abbey nearby avoided the fate of Hailes, because it was bought by the parishioners of Tewkesbury for a parish church.

After the Dissolution, the west range consisting of the Abbot's own apartments was converted into a house and was home to the Tracy family in the seventeenth century, but these buildings were later demolished and now all that remains are a few low arches in a meadow with outlines in the grass. Surviving remains include the small church for the disappeared parish, with unrestored medieval wall-paintings.

The abbey is now in the care of the National Trust and English Heritage.