The aim of this thesis is to explore the consequences of the Union of 1800 and to describe the economic, social and political changes in Ireland in the first half of the nineteenth century. I would like to examine the relationship of Britain and Ireland throughout the centuries, to find the roots and reasons for the problems and hostilities between the two countries. I will also try to summarize the economic, political and social background of the first half of the 19th century, and describe the causes and consequences of the worst disaster of Irish history, the Great Famine which has left its mark on the country in every field of life and led to the greatest immigration wave from Europe.