 Traditionally , Ireland is subdivided into four provinces : <unk> ( west ) , Leinster ( east ) , Munster ( south ) , and Ulster ( north ) . In a system that developed between the 13th and 17th centuries , Ireland has 32 traditional counties . Twenty @-@ six of these counties are in the Republic of Ireland and six are in Northern Ireland . The six counties that constitute Northern Ireland are all in the province of Ulster ( which has nine counties in total ) . As such , Ulster is often used as a synonym for Northern Ireland , although the two are not <unk> . 
