The Irish Sea separates the islands of Ireland and Britain. It is connected to the Atlantic Ocean by St George's Channel between Ireland and Wales in the south and by the North Channel between Ireland and Scotland in the north
The Isle of Man lies in the middle of the Irish Sea.
Ferry connections between Britain to Ireland via the Irish Sea include the routes from Swansea to Cork, Fishguard and Pembroke to Rosslare, Holyhead to Dún Laoghaire, Stranraer to Belfast and Larne, and Cairnryan to Larne. There is also a connection between Liverpool and Belfast via the Isle of Man.
The Irish Sea Forum is an environmental forum concerned with the Irish Sea.
The Irish Sea has been subject to heavy radioactive pollution by the first British weapons grade 239 plutonium nuclear production plant and power station at Windscale. An estimated 250 kg of plutonium have been deposited in marine sediments during the first decades of production.