Donegal is a large county located in the north-western fringe of the Isle of Ireland. It is isolated from the rest of the Republic of Ireland – to which it belongs – by a very long border with Northern Ireland, except for a very narrow strip of land in its southern part. However, the border has become invisible since the Good Friday agreements of 1998, which put an end to the Troubles in Northern Ireland. Donegal is a rural and sparsely populated county despite undeniable touristic assets whose economic vitality largely depends on trade with Northern Ireland. The prospect of the return of a hard border following Brexit has for the moment faded away with the displacement of the border in the Irish Sea. However, this is only a temporary provision which does not prevent its return in the long term. This would be a major obstacle to the economic development of the county and its inhabitants’ daily life, a sword of Damocles testifying to the geopolitical and geo-economic issues at stake in the British Isles because of Brexit and to the status of the borders between member states and external states.