The River Teifi (English: /ˈtaɪvi/ TY-vee; Welsh: Afon Teifi, pronounced [ˈavɔn ˈtɛivɪ]),[citation needed] formerly anglicised as Tivy,[4][5] forms the boundary for most of its length between the Welsh counties of Ceredigion and Carmarthenshire, and for the final 3 miles (4.8 km) of its total length of 76 miles (122 km), the boundary between Ceredigion and Pembrokeshire.

Over the next 30 miles (48 km), the Teifi meanders southwest in a gentle arc passing through Tregaron, Llanddewi Brefi, Cwmann, Lampeter, Llanybydder, Llandysul, Newcastle Emlyn, and Cenarth.

There is a large variety ranging from water-crowfoot to Atlantic salmon as well as otters, wetland birds and multi fruited river moss.

The resultant landform is one of gently rolling hills supporting a range of agriculture in which dairy and sheep farming dominate.

The very extensive raised mire above Tregaron acts as a huge sponge at the head of the river and evens out extremes in flow.

Rapids and waterfalls are uncommon but the examples at Henllan and, especially at Cenarth, are noteworthy and have been extensively photographed and painted because of the beauty of the landscape.

The Teifi has been designated as a Site of Special Scientific Interest (SSSI) since December 1997 in an attempt to protect the rare and unique features and species within it.

The catchment of the river is estimated to be 1,008 square kilometres (389 sq mi)[2] yielding an average flow at Glan Teifi, just upstream of Llechryd Bridge, of 29.126 m³/s.

Between Cenarth and Cardigan, there is an ancient tradition of fishing and travel using coracles – very simple light-weight boats made of bent sticks covered with waterproofed hide or skins.

In modern times, the river Teifi is still important to the population that surrounds it and currently serves as the complete water source for the local area of Mid & South Ceredigion.

[22] Further concern was reported by local press in March 2023 after 10 tonnes of debris and agricultural waste was pulled from a 3km stretch of the river in Llandysul.