Brecknockshire, also known as Breconshire or, in Welsh, as Sir Frycheiniog is an inland traditional county of Wales, bounded N. by Radnorshire, E. by Herefordshire and Monmouthshire, S. by Monmouthshire and Glamorgan, and W. by Carmarthenshire and Cardiganshire. Area 475,224 acres (1,923 km²). Population 56,000. The County is predominantly rural and mountainous. The Black Mountains occupy the SE of the County, the Brecon Beacons the central region, Fforest Fawr the SW and Mynydd Eppynt the North. Most of the Brecon Beacons National Park lies within the County. The highest point is Pen-y-Fan, 2907 ft (886 m). The River Wye traces nearly the whole of the N. boundary, and the Usk flows in an easterly direction through the central valley. Of the many waterfalls in the County, Henrhyd Falls are particularly spectacular. The main towns are Brecon, Brynmawr, Builth Wells, Hay-on-Wye, Llanwrtyd Wells and Ystradgynlais. The most important industries are agriculture, forestry and tourism.

Places of special interest: Brecon Beacons Mountains Centre, Libanus (SO0428); Brecknock Museum, Brecon (SN9726); Dan-yr-Ogof Caves, Glyntawe (SN8316); Tretower Castle and Court (SO1821); Y Gaer Roman Fort (SO0029).

The county is administered by Powys Council.