The National Eisteddfod of Wales (Welsh: Eisteddfod Genedlaethol Cymru) is the largest of several eisteddfodau that are held annually, mostly in Wales. Its eight days of competitions and performances are considered the largest music and poetry festival in Europe. Competitors typically number 6,000 or more, and overall attendance generally exceeds 150,000 visitors. The 2018 Eisteddfod was held in Cardiff Bay with a fence-free 'Maes'. In 2020, the event was held virtually under the name AmGen; events were held over a one-week period.
The National Museum of Wales says that "the history of the Eisteddfod may [be] traced back to a bardic competition held by the Lord Rhys in Cardigan Castle in 1176", and local Eisteddfodau were certainly held for many years prior to the first national Eisteddfod. Even before they became a regular annual event, Eisteddfodau were held on a national scale in Wales, such as the Gwyneddigion Eisteddfod of 1789, the Provincial Eisteddfodau from 1819 to 1834, the Abergavenny Eisteddfodau of 1835 to 1851, and The Great Llangollen Eisteddfod of 1858. However the National Eisteddfod of Wales as an organisation traces its history back to the first event held in 1861, in Aberdare.
One of the most dramatic events in Eisteddfod history was the award of the 1917 chair to the poet Ellis Humphrey Evans, bardic name Hedd Wyn, for the poem Yr Arwr (The Hero). The winner was announced, and the crowd waited for the winner to stand up to accept the traditional congratulations before the chairing ceremony, but no winner appeared. It was then announced that Hedd Wyn had been killed the previous month on the battlefield at Passchendaele in Belgium. These events were portrayed in the Academy Award nominated film Hedd Wyn.
In 1940, during the Second World War, the Eisteddfod was not held, for fear that it would be a bombing target. Instead, the BBC broadcast an Eisteddfod radio programme, and the Chair, Crown and a Literature Medal (as opposed to the usual Prose Medal) were awarded.