Thatcham is a market town and civil parish in the West Berkshire, England. It is situated in the valley of the River Kennet 3 miles (4.8 km) east of Newbury, 14 miles (23 km) west of Reading and 54 miles (87 km) west of London. The town has a long history dating back to prehistoric times, a claimant to the title of oldest continuously inhabited place in Great Britain. As of 2021, it had a population of 25,464, though it is part of a built-up area comprising itself and neighbouring Newbury of over 70,000 residents. It is on the route of the A4 Bath Road, the historic main road between London and Bristol.

The Kennet is a tributary of the River Thames in Southern England. Most of the river is straddled by the North Wessex Downs AONB. The lower reaches have been made navigable as the Kennet Navigation, which – together with the Avon Navigation, the Kennet and Avon Canal and the Thames – links the cities of Bristol and London.