Llanerchaeron, known as "Llanayron House" to its nineteenth-century occupants, is a grade I listed mansion on the River Aeron, designed and built in 1795 by John Nash for Major William Lewis as a model self-sufficient farm complex located near Ciliau Aeron, some 2+1⁄2 miles south-east of Aberaeron, Ceredigion, Wales. There is evidence that the house replaced an earlier mansion. A later owner, William Lewes, was the husband of Colonel Lewis's inheriting daughter.

The River Aeron is a small river in Ceredigion, Wales, that flows into Cardigan Bay at Aberaeron. It is also referred to on some older maps as the River Ayron.