The Isis is a traditional name used to refer to the upper section of the River Thames. This designation applies to the river from its source in the Cotswolds until it reaches the confluence with the River Thame at Dorchester-on-Thames in Oxfordshire. The name is deeply embedded in the local identity of the region.
As the river flows through the city of Oxford, the name "Isis" is frequently used in the context of local institutions, rowing clubs, and various city-based products. While the river is officially the Thames throughout its entire length, the historical use of the name Isis remains a significant cultural marker for the area surrounding Oxford.