The River Aeron (afon Aeron in Welsh) is a small river in west Wales that flows into Cardigan Bay at Aberaeron. It is also referred to on some older maps as the River Ayron.
It has its source in a range of rolling hills at grid reference SN620670 east of Hafod Ithel. One of the main sources is the mineral spring at Ffynnon Drewi above Llangeitho. It then follows a more or less westerly and then north westerly track to the sea. It has a rather broad valley bounded by low hills and has relatively few significant tributaries. Those that it does have include the Gwenffrwd, Nant Wysg, Nant Picadilly, Nant y Wernen and Nant Rhiw Afallan. The Afon Mydyr drains an area of old woodlands and dairy farming and includes the old farm of Rhiwbren Fawr.
On its way to the sea, the Aeron passes through Felinfach and by the village of Ciliau Aeron. It passes close to the restored mansion at Llanerchaeron which is now in the care of the National Trust before entering the picturesque town of Aberaeron where it enters the sea.
Despite the relatively small size of the river, it sustains a population of salmon and brown trout.
Although the Aeron has suffered from intermittent pollution including some severe incidents in the 1970s caused by creamery waste and crude sewage escapes in the Felinfach area, the principal impacts are now diffuse agricultural waste, pesticides from agriculture and acidification especially from upland forestry plantations.