an extraordinary Roman magistrate, appointed to guide the helm of state in the interval that elapsed between the death of one king and the election of his successor. That interval was called an interregnum. After the death of Romulus, ten of the leading senators were empowered to form themselves into a board or committee, for the purpose of nominating a successor to the vacant throne, and carrying on the government till their choice was approved by the people. These ten senators were called interreges, and each of them was entitled to hold the sovereign power, and enjoy its outward symbols and badges for five days in rotation. As soon as they had fixed upon a nominee their duty was to lay the matter before the senate. If the senate approved their choice, a meeting of the curia was then called, and the sense of the people taken. If the people were pleased with the nominee of the senate, a special law was passed by which the regal power was vested in him, and the interregnum came to a close. But if the people refused to ratify the choice of the senate, the interreges resumed office, and held it in rotation as before till a king was finally appointed.

Under the republic interreges were very frequently chosen to hold the consular comitia, when the existing consuls were not on the spot to do so themselves. As in the days of the monarchy, they were ten in number, and held office each for five days in rotation. They were selected from among the patrician members of the senate, and even after plebeians became eligible to nearly all the offices of state, they were never made interreges. On this account, an interregnum was always distasteful to the plebs, and their tribunes seldom failed to protest against and oppose it. After the second Punic War the custom of an interregnum fell almost wholly into abeyance. In the course of the first century B.C., only two instances of it are recorded.