River Thame

The River Thame /ˈteɪm/ is a river in Southern England. It is a tributary of the larger and better-known River Thames.

The general course of the River Thame is north-east to south-west and the distance from its source to the River Thames is about 40 miles (65 km). It flows through the English counties of Buckinghamshire and Oxfordshire.

The River Thame's source is several small streams which rise in the Vale of Aylesbury on the north side of the Chiltern Hills. These streams converge north-east of Aylesbury, the county town of Buckinghamshire. Aylesbury played an important role in the English Civil War when John Hampden (the town's Member of Parliament) defended Aylesbury at the Battle of Holman's Bridge, which crosses the Thame to the north of Aylesbury, in 1642.

The vale streams converge very close to the new village of Watermead. After leaving Watermead, the River Thame flows through farmland passing the small villages of Nether Winchendon and Chearsley before reaching the market town of Thame with which it shares its name. Thame is about 15 miles (24 km) east of Oxford and grew from an Anglo-Saxon settlement beside the river. In Anglo-Saxon times, Thame was in the Diocese of Dorchester.

From the town of Thame, the River Thame swings southward and after passing the villages of Great Milton and Stadhampton, its valley widens out. In this area in 1642 and 1643, the river acted as an important line of defence for Royalist Oxford. The bridges at Wheatley, Cuddesdon Mill and Chiselhampton were key crossing points, with Chiselhampton Bridge playing a critical part in Prince Rupert's movements before and after the Battle of Chalgrove Field.

The River Thame then reaches the small town of Dorchester, Oxfordshire (not to be confused with Dorchester, Dorset). There was a Romano-British settlement here and the town itself is of Anglo-Saxon origin. The Saxon cathedral in Dorchester was later superseded by Dorchester Abbey, which is preserved.

Just over half-a-mile (approx 1 km) south of Dorchester, the River Thame flows into the River Thames. The confluence is ⅔ of a mile (1 km) downstream of Day's Lock.

According to some usage, the River Thames is named the River Isis until its confluence with the River Thame. Ordnance Survey maps label the Thames as "River Thames or Isis" upstream of Dorchester. For more information on this issue see Etymology in the River Thames article.