The Black Mountains occupy the southeast of the area, the Brecon Beacons the central region, Fforest Fawr the southwest and Mynydd Epynt the north.

The River Wye traces nearly the whole of the northern boundary, and the Usk flowed in an easterly direction through the central valley.

The largest of these were the Lordship of Brecknock, which had its roots in the medieval Welsh kingdom of Brycheiniog, and the cantref of Buellt.

It often acted as a buffer state between England to the east and the powerful south Welsh kingdom of Deheubarth to the west.

The exact origins of Brycheiniog are unclear but the name is thought to derive from Brychan mac Anlach, the 5th century ruler of the area.

Unlike most cantrefs, it was not part of any of the major Welsh kingdoms for most of its history, but was instead ruled by an autonomous local dynasty.

During the Norman invasion of Wales, the Marcher Lord Philip de Braose conquered Buellt around 1095.

In November 1282, Edward I overran Buellt as part of his final conquest of Wales and the cantref became a crown possession.

Bernard de Neufmarché was a minor Norman lord who rose to power in the Welsh Marches before successfully undertaking the invasion and conquest of the Kingdom of Brycheiniog between 1088 and 1095.

When Edward Stafford, 3rd Duke of Buckingham, was executed for treason, having been suspected of plotting against King Henry VIII, the Lordship was forfeited to the crown.

The areas combined were: "Brekenoke" (Brecknock), "Crekehowell" (Crickhowell) "Tretowre", "Penkelly", "Englisshe Talgarth", "Welsshe Talgarth", "Dynas", "The Haye" (Hay-on-Wye), "Glynebogh", "Broynlles" (Bronllys), "Cantercely" (Cantref Selyf), "Llando Blaynllynby", "Estrodewe", "Buelthe" (Builth), and "Llangors".

[3][5] Elected county councils were created in 1889 under the Local Government Act 1888, taking over administrative functions which had previously been performed by unelected magistrates at the quarter sessions.

Along Brecknockshire's southern border with Monmouthshire, there were four such urban sanitary districts which straddled the county boundary: Brynmawr, Ebbw Vale, Rhymney, and Tredegar.

Along Brecknockshire's southern boundary there were four communities that did not become part of Powys under the 1974 reforms: Penderyn went to the Cynon Valley district of Mid Glamorgan, Vaynor went to Merthyr Tydfil district of Mid Glamorgan, and Brynmawr and Llanelly both went to Blaenau Gwent.

Powys County Council established a Brecknockshire "shire committee" consisting of councillors elected for electoral divisions within the former Borough of Brecknock.

Brecknock Society and Museum Friends (Welsh: Cymdeithas Brycheiniog a Chyfeillion yr Amgueddfa), found in 1928, is a historical society that promotes "the study and understanding of the Archaeology, History, Geology, Natural History, the Arts and Literature of Wales, especially the historic county of Brecknock."

A Brecon Fringe Festival organises alternative free music in pubs, hotels, galleries and cafes in the town.

Hay-on-Wye is a destination for bibliophiles in the United Kingdom, with two dozen bookshops, many selling specialist and second-hand books.

Devised by Norman, Rhoda and Peter Florence in 1988, the festival runs for ten days from May to June.

The present building dates back to 1841 and was re-modelled by Owen Morris Roberts and is considered to be one of the finest chapel interiors in Wales.

St Mary's Church, Hay-on-Wye consists of a nave and chancel with a square embattled tower at the west end.

Separated by a deep dingle, which probably was formerly a moat, it is situated westward of the town upon an almost precipitous eminence, near to the River Wye.

St Edmund's Church, Crickhowell is a Grade II* listed building built in the early 14th century.

The county has four clubs affiliated to the Welsh Bowling Association: at Brecon, Talgarth, Builth Wells and Hay on-Wye.

Brecon Leisure Centre at Penlan has a swimming pool, gymnasium, ten-pin bowling and a climbing wall.

The Gwernyfed and Hay Leisure Centre at Three Cocks has a fitness suite, sports hall and multi-purpose floodlit pitch.

On establishment in 1889 the Breconshire County Council adopted the attributed arms of Brychan, fifth century founder of Brycheiniog.

Gareth Gwenlan OBE (b. Brecon 26 April 1937 - d. Herts 8 May 2016), television producer and director, best known for his work on shows such as The Fall and Rise of Reginald Perrin, To the Manor Born, Only Fools and Horses.

Roger Glover (b. Brecon 30 November 1945), musician, best known as the bassist for hard rock bands Deep Purple and Rainbow.

Sarah Siddons (née Kemble) (b. Brecon 5 July 1755 – d. London 8 June 1831), actress, was the best-known tragedienne of the 18th century.