Stratfield Mortimer is a village and civil parish, just south of Reading, in the English ceremonial county of Berkshire and district (unitary authority area) of West Berkshire.

The south and south-east half of the parish consists of farms with a small percentage of woodland and is bisected towards the middle of the whole area by the Foudry Brook and adjacent Reading to Basingstoke Line (two tracks) which is more than 40% on raised embankments but in the far south is in a cutting. The north-east of the parish is the most populated: and is not so semi-rural or rural in density; it is the part more often colloquially called Mortimer. This more outlet- and amenity-served part, traditionally known as Mortimer Common, is at the top of the hill in Stratfield Mortimer civil parish. The northwestern 5% of the land is Mortimer Woods or common land which blends into Wokefield Common - Mortimer Woods has a set of Scheduled Ancient Monuments - one large, steep Bronze Age round barrow and three further smaller bowl barrows.

The linear village of Stratfield Mortimer climbs Mortimer Hill which rises westward from the Foudry Brook. It has no fixed formal or historic boundaries with Mortimer Common.

The south boundary (all but south-west, see the county boundary on the map shown above) is the straight footpath, the Devil's Highway, the eastern part of the Roman road from London to Bath, which is marked out today from Bagshot, Surrey to the best-preserved Roman Wall, ruins of town (such as amphitheatre) of Calleva Atrebatum in Silchester, 2 miles (3.2 km) south-west of the village.