Meirionnydd is a coastal and moutainous region of North Wales. It has been a kingdom, a cantref, a district and, as Merionethshire, a county.
Meirionnydd was a sub-kingdom of Gwynedd, supposedly founded by Meirion, a grandson of Cunedda, a warrior-prince who brought his family to North Wales from what is now Clackmannanshire, probably in the early 5th century. His dynasty seems to have ruled there for the next four hundred years. The kingdom lay between the River Mawddach and the River Dovey, spreading in a north-easterly direction.
The cantref held the presumed boundaries of the previous kingdom. It was abolished in 1536.
Meirionnydd expanded its borders, as a county (both historic and administrative) under an anglicized name, to include the old cantrefi of Penllyn and southern Dunoding (the commotes of Ardudwy Uwch Artro and Ardudwy Is Artro).
Meirionnydd was one of five districts of Gwynedd, Wales from 1974 to 1996. The district comprised the majority of the administrative county of Merionethshire and reverted to the the Welsh spelling of the county's name.
The district was created by the Local Government Act 1972, and replaced the following local government areas of Merionethshire:
Meirionnydd District was abolished in 1996 by the Local Government (Wales) Act 1994, becoming part of the unitary authority of Caernarfonshire and Merionethshire, subsequently renamed Gwynedd. An area committee of Gwynedd Council now covers the area.