Thames Head is a group of seasonal springs that arise near the village of Coates in the Cotswolds, about three miles south-west of the town of Cirencester, in the county of Gloucestershire, England. The spring water comes from the limestone aquifers of the Cotswolds. One or more of these springs are traditionally identified as the source of the River Thames.

The River Thames, known alternatively in parts as the River Isis, is a river that flows through southern England including London. At 215 miles (346 km), it is the longest river entirely in England and the second-longest in the United Kingdom, after the River Severn.