Harefield Pit is a 1.8-hectare geological Site of Special Scientific Interest in Harefield in the London Borough of Hillingdon. It is located in a disused chalk quarry which has been partly filled in.
It is an important Tertiary site in the London Basin, which displays a sequence through the Upper Chalk, Reading Beds and London Clay. It is the only known source of charophytes in the Reading Beds, and these have potential for correlation with other localities in Europe.
Natural England has designated the condition of the site as "unfavourable declining" because the Reading Beds are not visible due to covering by vegetation. Harefield Pit is located behind Lovett Road and there is no public access.