The Holy Roman Empire (HRE; German: Heiliges Römisches Reich (HRR), Latin: Imperium Romanum Sacrum (IRS), Italian: Sacro Romano Impero (SRI)) was for about a millennium a realm in Central Europe under a Holy Roman Emperor. Its character changed during the Middle Ages and the Early Modern period, when the power of the emperor gradually weakened in favour of the princes. In its last centuries its character became quite close to a union of territories. The first emperor of the realm, which was later called Holy Roman Empire, who was not member of the Carolingian dynasty, was Otto I, crowned in 962. The last was Francis II, who abdicated and dissolved the Empire in 1806 during the Napoleonic Wars. In a decree following the 1512 Diet of Cologne, the name was officially changed to Holy Roman Empire of the German Nation (German: Heiliges Römisches Reich Deutscher Nation, Latin: Imperium Romanum Sacrum Nationis Germanicæ) .

The Empire's territorial extent varied over its history, but at its peak it encompassed the Kingdom of Germany, the Kingdom of Italy and the Kingdom of Burgundy; for much of its history the Empire consisted of hundreds of smaller sub-units, principalities, duchies, counties, Free Imperial Cities, as well as other domains. Despite its name, for most of its history the Empire did not include Rome within its borders.

The territories and dominion of the Holy Roman Empire in terms of present-day states comprised Germany (except Southern Schleswig), Austria (except Burgenland), the Czech Republic, Switzerland and Liechtenstein, the Netherlands, Belgium, Luxembourg, and Slovenia (except Prekmurje), besides significant parts of eastern France (mainly Artois, Alsace, Franche-Comté, Savoy and Lorraine), northern Italy (mainly Lombardy, Piedmont, Emilia-Romagna, Tuscany, and South Tyrol), and western Poland (mainly Silesia, Pomerania, and Neumark).