The Brecon Beacons (Welsh: Bannau Brycheiniog; [ˈbanai̯ brəˈχei̯njɔɡ] ^ⓘ) are a mountain range in Wales. The range includes South Wales's highest mountain, Pen y Fan (886 metres (2,907 ft)), its twin summit Corn Du (873 metres (2,864 ft)), and Craig Gwaun Taf (826 metres (2,710 ft)), which are the three highest peaks in the range. The Brecon Beacons have given their name to the larger Brecon Beacons National Park, and the range itself is therefore sometimes known as the Central Beacons to differentiate the two.

Bannau Brycheiniog derives from the Welsh bannau, "peaks" and Brycheiniog, the early medieval kingdom which covered the area. The English name is derived from the Welsh. This name is first attested in the sixteenth century in John Leland's 1536–1539 Itinerary of Wales. Under his description of the Brecknockshire landscape Leland states :

"Artures Hille is three good Welsh (almost five English) miles south west from Brekenok, and on the very top of the hill is a fair wellspring. This hill of some is counted the highest hill of Wales, and in a very clear day a man may see from it a part of Malvern Hilles, and Glocestre, and Bristow, and part of Devenshir and Cornwale. There be other diverse hills by Artures Hille, that which, with it, be communally called Banne Brekeniauc."

The name Brecon Beacons first occurs in the eighteenth century (as "Brecknock Beacons") and referred to the area around Pen y Fan (which itself was sometimes referred to as "the Brecknock Beacon"). For instance, Emanuel Bowen's A New and accurate map of South Wales (1729) labels the peak as 'The Vann or Brecknock Beacon', John Clark's 1794 General View of the Agriculture of the County of Brecknock refers to 'the Vann, or Brecknock Beacon, the undisputed sovereign of all the mountains in South Wales', and an 1839 tithe map of Cantref parish labels the mountain simply 'Beacon'. A slightly wider definition was used in 1809 by the Breconshire historian Theophilus Jones, who wrote that 'of the lofty summits of the Brecknock Beacons, that most southwards is the lowest, and the other two nearly of a height, they are sometimes called Cader Arthur or Arthur's chair'. This implies that "Brecknock Beacons" referred to only three summits, including Pen y Fan and Corn Du.

To distinguish the Brecons Beacons range from the national park, the range is sometimes called the "Central Beacons".

The Brecon Beacons comprises six main peaks, which from west to east are: Corn Du, 873 metres (2,864 ft); Pen y Fan, the highest peak, 886 metres (2,907 ft); Cribyn, 795 metres (2,608 ft); Fan y Bîg, 719 metres (2,359 ft); Bwlch y Ddwyallt, 754 metres (2,474 ft); and Waun Rydd, 769 metres (2,523 ft). These summits form a long ridge, and the sections joining the first four form a horseshoe shape around the head of the Taf Fechan, which flows away to the southeast. To the northeast of the ridge, interspersed with long parallel spurs, are four cirques (Welsh: cymoedd, sing. cwm) or round-headed valleys; from west to east these are Cwm Sere, Cwm Cynwyn, Cwm Oergwm and Cwm Cwareli.

The Brecon Beacons range, Fforest Fawr, and Black Mountain form a continuous massif of high ground above 300 metres (1000 feet). The A470 road forms an approximate boundary between the central Beacons and Fforest Fawr.

The Brecon Beacons National Park was established in 1957, the third of the three Welsh parks after Snowdonia in 1951 and the Pembrokeshire Coast National Park in 1952. It covers an area of 519 square miles (1,340 km²), which is much larger than the Brecon Beacons range. Over half of the park is in the south of Powys; the remainder of the park is split between northwestern Monmouthshire, eastern Carmarthenshire, northern Rhondda Cynon Taf and Merthyr Tydfil, and very small areas of Blaenau Gwent, and Torfaen.