Car hire at Belfast City Airport covers drivers who want to cross the border into the Republic of Ireland. Northern Ireland is in the UK and the Republic of Ireland is in the EU but, since Brexit, Northern Ireland has maintained a special status, which removes the need for a physical border checkpoint between the two jurisdictions. There is a common travel area and you can simply travel back and forth. However, it's important to let your car hire company know if you intend to cross from Northern Ireland to the Republic as they will need to extend your insurance cover to travel abroad - even though it won’t feel like a different country. Search rental cars on KAYAK