The date of the first Eisteddfod is greatly debated among scholars

Eisteddfod
The date of the first Eisteddfod is greatly debated among scholars, but boards for the judging of poetry has existed in Wales from as the twelfth century, and it is likely that the ancient Celtic bards had formalized ways of judging poetry as well. The first Eisteddfod can be traced back to 1176, under the auspices of Lord Rhys, at his castle in Cardigan. There grand gathering was held to which poets and musicians were invited from all over the country. A chair at the Lord's table was awarded to the best poet and musician. This is still the case in the modern day National Eisteddfod. Over time interest in the Welsh arts declined, and the standard of the main eisteddfod deteriorated as well and they became gradually more informal. In 1789, Thomas Jones organised an eisteddfod in Corwen where for the first time the public were admitted. The success of this event led to a revival of interest in Welsh literature and music.
Eisteddfod
An eisteddfod is a Welsh festival of literature, music and performance. The tradition of such a meeting of Welsh artists dates back to at least the 12th century, when a festival of poetry and music was held by Rhys ap Gruffydd of Deheubarth at his court in Cardigan in 1176 but, with the decline of the bardic tradition, it fell into abeyance. The present-day format owes much to an eighteenth-century revival arising out of a number of informal eisteddfodau. The word eisteddfod is derived from the Welsh word eistedd, meaning "to sit", and bod meaning "to be" and therefore means "to be sitting" or "to be sitting together" ("bod" is softly mutated into "fod").
Eisteddfod Revival
Iolo Morganwg (bardic name of Edward Williams) founded "Gorsedd Beirdd Ynys Prydain" (Gorsedd of the Bards of the Isle of Britain) in 1792 to restore and replace the ancient eisteddfod. The first eisteddfod of the revival was held in Primrose Hill, London.
"The Gentleman's Magazine" of October, 1792 reported on the revival of the eisteddfod tradition.
This being the day on which the autumnal equinox occurred, some Welsh bards resident in London assembled in congress on Primrose Hill, according to ancient usage. Present at the meeting was Edward Jones who had published his "The Musical and Poetical Reelicks of the Welsh Bards" in 1784 in a belated effort to try to preserve the native Welsh traditions being so ruthlessly stamped out by the new breed of Methodists.
The Blue Books' notorious attack on the character of the Welsh as a nation in 1846 led to public anger and the belief that it was important for the Welsh to create a new national image. By the 1850s people began to talk of a national eisteddfod to showcase Wales's culture. In 1858 John Williams ab Ithel held a "National" Eisteddfod complete with Gorsedd in Llangollen. "The great Llangollen Eisteddfod of 1858" was a significant event. Thomas Stephens won a prize with an essay demolishing the claim of John Williams (the events organiser) that Madoc discovered America. As Williams had expected Stephens's essay to reinforce the myth, he was not willing to award the prize to Stephens and, it is recorded, "matters became turbulent". This eisteddfod also saw the first public appearance of John Ceiriog Hughes who won a prize for a love poem, Myfanwy Fychan of Dinas Brân, which became an instant hit. There is speculation that this was a result of its depiction of a "deserving, beautiful, moral, well-mannered Welshwoman", in stark contrast to The Blue Books' depiction of Welsh women as having questionable morals.