Glascwm is a community in the upper Edw valley in Radnorshire, Powys, Wales.

The remainder of the population lives in scattered farms and dwellings and in the three rural settlements of Cregrina, Glascwm, Bettws Diserth and Llansantffraed-in-Elwel.

[2] A Clas community (352 A.D.) was established in Glascwm within the cantref (medieval Welsh land division) of Elfael, (one of a number of Welsh kingdoms occupying the region between the River Wye and River Severn), possibly as early as the 6th century.

[3] Glascwm was also the location of a miraculous hand-bell mentioned by Giraldus Cambrensis (Gerald of Wales) in the late 12th century.

[3] In the late 13th century, Glascwm was one of several places in the region for which Thomas, Bishop of St David's granted the right to the Lord of The Manor to hold a market or fair.