The first record of a church on this site comes from around 800 AD. The Doomsday book (1086) records a priory of 24 Canons dating from the reign of Edward the Confessor. The church was rebuilt, starting in 1094. legend says that the Dean of Twynham, the original name of the town, tried to move the church to an alternative site, but the building materials mysteriously moved back to the original site each night. Eventually, the Dean took this as a message from God that he didn’t want the church to be moved and it was built on the original site. Another legend says that in 1150, during further building works a carpenter cut a beam too short. these beams were very expensive and it caused great consternation. The workers left for the day and were amazed when they returned the next day to find the beam in place in the roof and restored to the correct length. The name of the town, as the legend goes, was changed from Twynham to Christchurch in recognition of this miracle. It was at this time that the priory was refounded, having seemingly ceased to operate some time since the doomsday record, 60 years earlier. In 1303, the patronage of the priory passed to the crown and then in 1330 to the Earl of Salisbury, which marked another major round of building with new chapels and chances to the roof and entrance porch. This work was finally completed in the early 15th century. It is not recorded why but the Norman Tower was replaced in the late 15th century. This may have been due to the collapse of the original tower. By this time, the priory church looked much as it does today.
The priory was surrendered to the crown in November 1539. The prior was given a pension and a house to live in for the rest of his life. It was decided to clear the whole site, but a petition from the townspeople to the king resulted in the church being left in place as the town’s parish church. very little of the priory buildings can be seen in the church’s environment and is evidence of the complete destruction of the priory buildings.