 In 1798 , members of the Protestant <unk> tradition ( mainly Presbyterian ) made common cause with Roman Catholics in a republican rebellion inspired and led by the Society of United <unk> , with the aim of creating an independent Ireland . Despite assistance from France the rebellion was put down by British and Irish government and yeomanry forces . In 1800 , the British and Irish parliaments both passed Acts of Union that , with effect from 1 January 1801 , merged the Kingdom of Ireland and the Kingdom of Great Britain to create a United Kingdom of Great Britain and Ireland . 
