Machynlleth, sometimes referred to colloquially as Mach, is a market town and community in Powys, Wales and within the historic boundaries of Montgomeryshire. It is in the Dyfi Valley at the intersection of the A487 and the A489 roads. At the 2001 Census it had a population of 2,147.
Machynlleth was the seat of Owain Glyndŵr's Welsh Parliament in 1404, and as such claims to be the "ancient capital of Wales". However, it has never held any official recognition as a capital. It applied for city status in 2000 and 2002, but was unsuccessful. It is twinned with Belleville, Michigan.
Machynlleth hosted the National Eisteddfod in 1937 and 1981.