The Céide Fields (Irish: Achaidh Chéide, meaning "flat topped hill fields") is an archaeological site on the north County Mayo coast in the west of the Republic of Ireland, about 8 kilometres northwest of Ballycastle. The site is the most extensive Neolithic site in the world and contains the oldest known field systems in the world. Using various dating methods, it was discovered that the creation and development of the Céide Fields goes back some five and a half thousand years.