This research project was designed to investigate the nature, development and impact of the Dublin nationalist press in the mid-nineteenth century. The prime focus was placed upon the period between 1842 and 1865 beginning with the foundation of The Nation newspaper that heralded a new era of Irish constitutional nationalism, and ending with the suppression of The Irish People, a revolutionary newspaper that fmnly established the presence of a long-term advanced Irish nationalist press. The overriding aim of the Dublin nationalist press was to overthrow the 1800 Act of Union and achieve political autonomy for Ireland. During this period the Famine occurred, an event which exerted a crucial impact on Irish nationalist thinking. Within this context, this thesis draws upon critical analyses of the journalistic and literary contents of the Dublin nationalist newspapers in order to assess their effect upon the development of Irish nationalism. The most influential newspapers in the Irish nationalist movement were published in Dublin, and it was the base from where the most important Irish nationalists conducted their political campaigns. Above all, a key aim of this thesis was to assess the role of the Dublin nationalist press in influencing and reflecting both the constructive and destructive nature of Irish nationalism. With this in mind, an emphasis was placed upon . the power of ideas articulated in the Dublin nationalist press, particularly the impassioned dynamics between constitutional nationalism and revolutionary nationalism. This research also focuses upon the thinking of the high-profile individuals who were involved with the Dublin nationalist newspapers, and the inspiration they gave to their contemporaries and future Irish nationalists. Based upon extensive newspaper and manuscript sources, this thesis establishes that what was written in the Dublin nationalist press during the mid-nineteenth century had a powerful and lasting effect on the development of Irish nationalism. Presenting the first defInitive analysis of the relationship between the Dublin nationalist press and the ideological development of Irish nationalism during the mid-nineteenth century, and providing in-depth critical analysis of the propaganda espoused by these newspapers, this thesis offers another much-needed contribution to the important but neglected area of the Irish nationalist press in the nineteenth century.