In 1690, as his father's heir, he was elected King of the Romans. During the last years of his father's long reign, in preparation for his assumption of power, he began to build his own party of younger men, which included Prince Eugene de Savoie, who favoured a more assertive policy.

On 24 February 1699, in Vienna, he married Princess Wilhelmine Amalie of Brunswick-Lueneburg. They became the parents of two daughters and one son, Leopold Josef, the latter died only nine-months old.

In 1705 he succeeded his father as Emperor of the Holy Roman Empire and installed his 'Young Party' in government. A vigorous ruler, he was determined to reassert imperial rights in Germany and Italy, which his father had neglected. This involved the imposition of the ban of the empire against the electors of Bavaria and Cologne, who had allied with France in the War of the Spanish Succession. This and other examples of his energetic imperial policy aroused growing suspicion among the German rulers. He also reasserted his rights over the German Catholic Church and this, together with his territorial ambitions in Italy, brought him into conflict with the papacy.

A lively man with a love of ceremonial and an elevated concept of his office, he died suddenly from smallpox in 1711, aged only thirty-two. He had been violent, with intelligence below the mediocre,
his death was much more meaningful than his life had been, for, as Josef left only daughters, his younger brother became Emperor.

Source: Leo van de Pas