Trewern is a small village, community and electoral ward in Montgomeryshire, Powys, Wales.

The community includes the villages of Buttington and Middletown, situated 4.5 miles (7.2 km) northeast of Welshpool, 14.5 miles (23.3 km) west of Shrewsbury and 1 mile (1.6 km) west of the Wales-England border.

It is situated on the A458 road, between the towns of Newtown, Shrewsbury and Welshpool.

Although only a small village in terms of population, there is a primary school, Ysgol Gynradd Buttington Trewern, with pupils travelling from miles around.

Trewern also has many other sites, such as an extinct volcano in form of Moel y Golfa, Cefn y Castell and Breidden Hill Trewern Hall is a half-timbered house in the village dating from the late 16th century.