Rhandirmwyn is a small community in the upper Tywi Valley in Carmarthenshire. The River Tywi runs a mere 500 meters from Rhandirmwyn. The town is nestled in the Cambrian Mountains and lies just south of Pen y Darren, noted for having a first century Roman fort, and to the west of Nant Gwyn.

It's name is derived from the joining of two words, namely, 'Rhandir,' which means an area of land and 'Mwyn,' which means mineral. So, translated the name means exactly that, a piece of land that contains minerals – in this case Lead and Zinc.

Rhandirmwyn effectively extends along both sides of the Tywi River, some two miles north of Cilycwm village and extends up the Gwenffrwd valley towards Cwrt-y-Cadno as far as Bwlchyrhiw and then east across the mountains into Ceredigion and Breconshire (Powys). Llyn Brianne Reservoir is located above the town and around this delightful reserve is the circular dinas walk. This walk is steep and difficult in a couple of locations but is generally a pleasant walk and passes through mature oak woodland alive in the summer with hundreds of pied and spotted flycatcher, wood warbler, blackcap and willow warbler to name but a few.

During the early part of last century Red Kites could only be seen occasionally in the Tywi Valley around Rhandirmwyn, then, this was the only place in Britain where they could be seen. Now however red Kites are a big attraction and can be seen on a daily basis flying above Rhandirmwyn.