Hanover
In 1636 George, Duke of Brunswick-Lüneburg, ruler of the Brunswick-Lüneburg principality of Calenberg, moved his residence to Hanover. The Dukes of Brunswick-Lüneburg were elevated by the Holy Roman Emperor to the rank of Prince-Elector in 1692, and this elevation was confirmed by the Imperial Diet in 1708. Thus the principality was upgraded to the Electorate of Brunswick-Lüneburg, colloquially known as the Electorate of Hanover after Calenberg's capital (see also: House of Hanover). Its electors would later become monarchs of Great Britain (and from 1801, of the United Kingdom of Great Britain and Ireland). The first of these was George I Louis, who acceded to the British throne in 1714. The last British monarch who ruled in Hanover was William IV. Semi-Salic law, which required succession by the male line if possible, forbade the accession of Queen Victoria in Hanover. As a male-line descendant of George I, Queen Victoria was herself a member of the House of Hanover. Her descendants, however, bore her husband's titular name of Saxe-Coburg-Gotha. Three kings of Great Britain, or the United Kingdom, were concurrently also Electoral Princes of Hanover.

Q: Who confirmed the elevation of the Dukes of Brunswick-Lüneburg in 1708?
Imperial Diet