Hormer was an ancient hundred of Berkshire, England.
It consisted of the area immediately west of Oxford within the bend of the River Thames, all of which was transferred to Oxfordshire on 1 April 1974 in accordance with the Local Government Act 1972.
It included the ancient parishes of The hundred also included the almost uninhabited extra-parochial area of Bagley Wood, which became a civil parish in 1858 and was joined to Radley in 1900.
[1] The name of the hundred is derived from what was presumably its original meeting place, an unidentified Horningamere "pool of the Hornings".
The court of the hundred met at Bagley Wood, and later at Cumnor.