The Empire of Charles V, also known as the Habsburg Empire, included the Habsburg hereditary lands in central Europe, the kingdoms of Spain, the colonial Spanish Empire, the kingdom of Naples, the Habsburg Netherlands and other territories and principalities across Europe. It is sometimes considered to include, in addition, the kingdoms of Bohemia and Hungary which were held by Charles's brother Ferdinand during his reign. Charles was also Holy Roman Emperor and, as such, was suzerain of the states of the Holy Roman Empire.
The empire was the first to be labelled as "the empire on which the sun never sets", a term used to describe several global empires throughout history. The lands of the empire had in common only the monarch, Charles V, while their boundaries, institutions, and laws remained distinct. Charles's nomenclature as Holy Roman Emperor was Charles V (also Karl V and Carolus V), though earlier in his life he was known by the names of Charles of Ghent (after his birthplace in Flanders), Charles II as Duke of Burgundy, and Charles I as King of Spain (Carlos I) and Archduke of Austria (Karl I). The imperial name prevailed due to the politico-religious primacy held by the Holy Roman Empire among European monarchies since the Middle Ages, which Charles V intended to preserve as part of his (ultimately failed) project to unite Christendom under his leadership.