The River Ithon is a major left-bank tributary of the River Wye

River Wye

The River Wye is the fifth-longest river in the UK and for parts of its length forms part of the border between England and Wales. It is important for nature conservation and recreation.-Description:...

 in Powys

Powys

Powys is a local-government county and preserved county in Wales.-Geography:Powys covers the historic counties of Montgomeryshire and Radnorshire, most of Brecknockshire , and a small part of Denbighshire — an area of 5,179 km², making it the largest county in Wales by land area.It is...

, mid Wales

Wales

Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

. It rises in the broad saddle between the western end of Kerry Hill and the hill of Glog to its west and flows initially southwards to Llanbadarn Fynydd. It then takes a twisting route south via the villages of Llanbister, Llanddewi Ystradenni and Penybont

Penybont

Penybont is a small village in Powys, Wales.- Location :It is located to the east of Crossgates, and to the north-east of Llandrindod Wells. The A44 runs east-west through the village, and the A488, which starts in Penybont, runs north to Knighton and Shrewsbury...

 before turning southwest, then doubling back northwards towards Crossgates

Crossgates, Powys

Crossgates is a village in Powys, Wales with an approximate population of 400. It is located three miles northeast of Llandrindod Wells and eight miles southeast of Rhayader, at the point where the A483 and A44 roads intersect. It is notable as the site of a busy service station.-Facilities:The...

. From here it resumes a southwesterly course, flowing past Llandrindod Wells

Llandrindod Wells

Llandrindod Wells , colloquially known locally as "Llandod", is a town and community in Powys, within the historic boundaries of Radnorshire, mid Wales, United Kingdom. It was developed as a spa town in the 19th century, with a boom in the late 20th century as a centre of local government. Before...

 to a confluence with the Wye, 1 mile to the south of Newbridge-on-Wye

Newbridge-on-Wye

Newbridge-on-Wye is a small village in Powys, Wales. It lies, as its name suggests, on the River Wye, just downstream from the market town of Rhayader.- Location :...

.