River Tywi

River Tywi (Towy)
River
Course of the River Tywi
Cities	Llandovery, Llandeilo, Carmarthen
Source
- location	Cambrian Mountains (SN802631)
- elevation	488 m (1,601 ft)
Mouth	Carmarthen Bay
Length	120 km (75 mi)
Basin	515 km2 (199 sq mi)
Discharge
- average	45 m3/s (1,589 cu ft/s)

The River Towy or Tywi (Welsh: Afon Tywi) is one of the two longest rivers flowing entirely within Wales, (the other is the River Teifi) with a total length of 120 km (75 mi). It is noted for its sea trout and salmon fishing.

The river rises within 15 km (9.3 mi) of the Teifi on the lower slopes of Crug Gynan in the Cambrian Mountains and, flowing through the steep, rugged hills of the Towy Forest, forms the border between Ceredigion and Powys. The river flows generally south-westwards through Carmarthenshire passing through the towns of Llandovery and Llandeilo. In Carmarthen it is joined by a substantial tributary, the Afon Gwili, at Abergwili. Finally the Towy flows into Carmarthen Bay east of the Pendine Sands in an estuary which it shares with the River Taf and the two branches of the River Gwendraeth. The mouth of the Towy estuary is guarded by Llansteffan Castle, a 12th-century Norman castle.

The Towy's numerous tributaries include the Cothi, Gwili, Brân, and Doethie.

The Tywi's total length is 120 km (75 mi).