Pseudonym of Edward Williams, renowned forger and collector of medieval Welsh documents, and godfather of the mesodruid phenomenon, which was greatly influenced by his involvement with Freemasonry. His "bardic" name is translated as "Ned of Glamorgan", as he was from Llancarfan, in Glamorgan. He claimed to have manuscripts which proved that Druidism and the bardic tradition had continued unmolested in Glamorgan since the days before the Romans, through the introduction of Christianity, and into the modern era. He was wrong. Morgannwg had the fear that the Welsh were losing their heritage and traditions, and so felt he had to preserve and reintroduce them to the public. Unfortunately, some of this task involved forging documents and creating traditions.
Born in 1747, he was trained to follow his father in the masonry business; it's also likely that he was a Freemason, which influenced his establishment of the Gorsedd. After he moved to London in 1770, he quickly took to mesodruidism, which had been flourishing for seventy-five years.
Always in bad health, he moved back to Glamorgan in 1777, and took to various odd jobs: mason, shopkeeper, surveyor. Eventually, surveying took him under the wing of the antiquarians, and it's them who we have to thank for introducting Iolo to the art of "preservation."
In 1792, he created the Gorsedd, an essembly of Welsh poets, which merged with the Eisteddfod, created by his rival William Jones. He also contributed certain ceremonial aspects to the Eisteddfod, likely culled both from his own imagination and the Masons.
He had a hand in The Myvyrian Archaiology, one of the earliest printed collections of medieval Welsh literature; unfortunately, some of the works were his forgeries, including poems attributed to Iolo Goch and Dafydd ap Gwillim, as well as an extra third of the Welsh Triads. Morgannwg was actually a collector and copier of manuscripts, however; some of the items found in his papers can be found in authentic manuscripts of various dates, such as his version of the Hanes Taliesin, and certain poems. Some of these papers were collected in The Iolo Manuscripts, edited by his son Taliesin Williams, who unfortunately didn't realize how much his father had actually invented. It was from these manuscripts that Lady Charlotte Guest culled most of her notes from when she was translating the Mabinogion from the Red Book of Hergest. However, she did not rely on any of his transcriptions of the Mabinogion, except for the "Taliesin" episode.
He is also the source for the spurious Barddas, which claims to be the work of one Llewellyn Sion in the sixteenth century, recording the beliefs of the ancient bards and their history. Even if his manuscript is authentic, it is still only from the sixteenth century, and hardly representative of the beliefs of the bards from ancient times to the beginning of the sixth century, much less represent a continuation to the eighteenth century.
Reportedly, he had a heavy laudanum habit, and so much of those forgeries were made under what may have been a sincere--though misguided--effort to "preserve" Welsh tradition.
After his death, his son Taliesin Williams collected Iolo's papers and published them as Iolo Manuscripts: A Selection of Ancient Welsh Manuscripts (1848). The intent was to act as a companion to the Myvyrian Archaiology (and perhapse timed to coincide with Lady Guest's publishing of The Mabinogion). Unfortunately, like the MA, it was a mix of Iolo's forgieries and legitimate copies of old Welsh literature, and only within the last fifty years have scholars been able to distinguish between the two. Most egregious is the inclusion of "Rhys Goch of Tir Iarll"--a bard who never existed, but was the result of Iolo's forgeries.
He died December 18, 1826, and is buried in Flemingston with his family.
Morgannwg was actually a rather gifted poet who understood his subject; if he had stayed on the straight and narrow, we may be thinking of him less as forger and more as a Blakeian visionary.