The Afon Teifi is a Welsh river flowing approximately 75 miles (121 km) through the counties of Ceredigion and Pembrokeshire, from its source at the Teifi Pools in central Wales to its mouth at Cardigan Bay on the west coast. It is one of the longest rivers found entirely in Wales. The upper reaches are oligotrophic in character, while the lower sections are predominantly mesotrophic. The river flows over hard rock and features some spectacular steep-sided gorges in the lower section, most notably the Cilgerran Gorge near Cardigan town. The river has a spatey flow regime, meaning water levels can rise and fall quickly.

No licence is required to paddle the Teifi. The river is graded 1/2 for most of its length, with short sections reaching grade 3–5. The stretch from Llandysul to Cenarth Falls is a documented paddling route, and the lower section from Llechryd Bridge (SA43 2QA) to Patch Beach (SA43 1PP) covers approximately 7 miles one-way and takes 2–3.5 hours. This lower stretch passes through the Cilgerran Gorge and includes historic castles and woodland. The river becomes tidal below Llechryd. On the tidal estuary, a 5 mph speed limit is enforced through the moorings at St Dogmaels and Netpool up to Cardigan old bridge. The Patch pontoon has been closed until further notice and should not be used; the pontoon at St Dogmaels is the primary access point in that area. Sandbanks in the estuary are noted to shift, and paddlers are advised to check the deep-water channel at low water before venturing into the tidal section.

The river is designated a Special Area of Conservation and supports a diverse range of wildlife including otters, Atlantic salmon, sea trout, brown trout, river lamprey, and bullhead. The in-stream vegetation is dominated by water-crowfoot and water-starworts, characteristic of oligo-mesotrophic base-poor rock rivers. A small traditional coracle fishery operates on the river, targeting salmon and sea trout. The Teifi is considered a challenging touring river and is recommended for experienced groups, including those undertaking Duke of Edinburgh Gold Award expeditions.