A Reichsverweser (German pronunciation: [ˈʁaɪ̯çsfɛɐ̯veːzɐ]) or imperial regent represented a monarch when there was a vacancy in the throne, such as during a prolonged absence or in the period between the monarch's death and the accession of a successor. The term Verweser comes from the Old High German firwesan and means "for or in the place of a person". The plural form is the same as the singular.

In the Holy Roman Empire, Reichsverweser were used periodically, but after its dissolution in 1806, the position was occupied only for one relatively short period during the German revolutions of 1848–1849. Although there were discussions about naming a Reichsverweser at the end of World War I and during the Nazi era, none was ever appointed.

Positions similar to Reichsverweser have been used in Hungary, where they are called kormányzó, in Finland (valtionhoitaja) and in Sweden (riksföreståndare).

In the Holy Roman Empire's German and Italian territories, regents were called imperial vicars (Reichsvikare). For Germany, the Golden Bull of 1356 formally codified an earlier rule on imperial administration: the Count Palatine of the Rhine was imperial vicar for the territories under the Frankish civil law code (Salic Law), while the Elector of Saxony was vicar for the territories under Saxon law. Their powers included continuing the king's ongoing business, jurisdiction over the courts and granting certain imperial fiefs.

The imperial vicariate over Italy, which the popes at times claimed as their right, was disputed between the dukes of Savoy and Mantua. During the frequent absences of Emperor Frederick II in the 13th century, he appointed imperial governors (Reichsgubernatoren) as deputies and guardians for his sons Henry (VII) and Conrad IV.

On 28 June 1848, four months after the outbreak of the German revolutions of 1848–1849, the Frankfurt National Assembly created a Provisional Central Authority (Provisorische Zentralgewalt) that was to take over the management of the executive branch for all of Germany until a constitution was adopted and a final head of state appointed. On the following day, Archduke John of Austria was elected Reichsverweser, an office that he was intended to hold until the National Assembly appointed an emperor as head of state. The power of John's government was limited, since the larger individual states in particular cooperated with it only when it suited their interests. Executive power remained with the individual states. After the revolution was suppressed in the summer of 1849, the Provisional Central Authority remained in office. It was not until 20 December 1849 that John transferred his powers to an Austro-Prussian Federal Commission (Bundeszentralkommission).

In the final weeks of World War I, calls increased for the abdication of Prussian King and German Emperor Wilhelm II. Walter Simons, an advisor to Chancellor Max von Baden on international issues, thought that Wilhelm and the unpopular crown prince should abdicate so that a regency council could be established for the next heir to the throne, the then 12-year-old Wilhelm of Prussia. A law amending the constitution of the German Empire would have been needed to establish a Reichsverweser. Wilhelm II rejected the idea on 1 November 1918.

When the Social Democratic Party demanded the emperor's abdication, von Baden urged him plainly to step down. On 9 November 1918 he announced the abdication of Wilhelm II and the crown prince on his own authority. He thought that the abdication was imminent and that officials were simply working out the formulation of the announcement. He also feared that a revolution was imminent.