Mostyn is a village and community in Flintshire, Wales, and electoral ward lying on the estuary of the River Dee, located near the town of Holywell. It has a privately owned port that has in the past had a colliery and ironworks and was involved in the export of commodities, and in present times services the offshore wind industry and ships the wings for the Airbus A380 which are manufactured at Broughton.

The River Dee is a river flowing through North Wales, and through Cheshire, England, in Great Britain. The length of the main section from Bala to Chester is 113 km and it is largely located in Wales. The stretch between Aldford and Chester is within England, and two other sections form the border between the two countries.