In prehistory the area was probably fairly heavily wooded with a lake and a marshy area. The Domesday Book of 1086 does not record Hartley Wintney by name. Both before and after the Norman conquest of England it was probably part of the royal manor of Odiham.
The earliest record of Hartley Wintney by name is from the 12th century, when Wintney Priory of Cistercian nuns was founded there. In the 13th century its toponym was variously recorded as Hercelega, Hurtlegh or Hertleye Wynteneye. This last version means "forest clearing where the deer graze by Winta's island". Winta was probably a Saxon who held the island in the marshes. The toponym was recorded as Hurtleye Winteney or Wytteneye in the 14th century and Herteley Witney in the 16th century.
About 100 years after the Norman conquest Hartley Wintney was made a separate manor held by the FitzPeter family. It was Geoffrey FitzPeter who founded the Cistercian priory. A deer park stretched from Odiham to the outskirts of the settlement and to the north. It was used for 600 years by royalty and others for hunting, and its wood was used for fuel.