This is a translation of the 1867 work by Alexander Hold, 'Geschichte der Feldzugs in Italien 1866', which describes in detail the campaign of the previous year, fought between the armed forces of the Austrian empire and the kingdom of Italy in the Austrian province of Venetia, the southern Tyrol and on the Adriatic Sea. The author served in the Engineers during the Campaign of 1859, and during the Campaign of 1866 was a Captain present with the Austrian headquarters throughout the Custoza campaign. As such he was ideally placed to provide a detailed account of his countrymen's efforts - he was a firsthand observer and would have taken part in discussions of Austrian strategic planning before and during it. Moreover, since he was on the staff he would have immediate knowledge of the other aspects of Austrian staff work of the period, the administration of the railways and telegraphs and the collection of intelligence. As a result, Hold's views about the forces of the participants, his comments on the terrain of the theatre of war and his assessment of the correct and incorrect decisions made by the Austrian and Italian high commands are of considerable interest because they shed informed light on what is the often forgotten part of the 1866 war, and a close study of his figures and assessments will repay all students of this campaign. This new translation by Stuart Sutherland, who also supplies extensive explanatory notes, is an important contribution to the literature available for this most interesting and important 19th Century campaign, providing a very detailed account not only of the principal Battle of Custoza, but also the Campaign in the Tyrol, and the naval war in the Adriatic that culminated in the Battle of Lissa.