The princeps senatus was not a lifetime appointment. He was chosen by every new pair of
censors (that is, every 5 years). Censors could, however, confirm a princeps senatus for a period of another 5 years. He was selected from
patrician senators with
consular rank, usually former censors. The successful candidate had to be a patrician with an impeccable political record, respected by his fellow senators.
The office was established around the year 275 BC.
 Originally, the position of the princeps was one of honor: he had the privilege of speaking first on the topic presented by the presiding
magistrate. This gave the position great dignitas as it allowed the princeps to set the tone of the debate in the Senate. Across the 3rd and 2nd centuries BC, the office gained the prerogatives of the presiding magistrates and additional privileges, namely:
- Summoning and adjourning the Senate;
- Deciding its agenda;
- Deciding where the session should take place;
- Imposing order and other rules of the session;
- Meeting, in the name of the Senate, with embassies of foreign countries; and
- Writing, in the name of the Senate, letters and dispatches.
By 80 BC, it is believed that the status and function of the office was changed by the
constitutional reforms of Lucius Cornelius Sulla. Although the term remained, reflecting the
senator who was named first in the roll of the
Senate issued by the Censors, the prerogatives of the office were restricted. In particular, the honor of speaking first on any topic debated in the Senate, a measure of their
political clout, was removed from them and transported to the
After the fall of the
Roman Republic, the princeps senatus was the
Roman Emperor, and during the period of the
Principate, no other individual is believed to have held the office (see also:
princeps). However, in the emperor's absence, it is possible that a Senator was granted the privilege of holding this role when the Senate met; the notoriously unreliable
Historia Augusta claimed that during the
Crisis of the Third Century, some others held the position; in particular, it stated that the future emperor
Valerian held the office in 238, during the reigns of
Maximinus Thrax and
Gordian I, and he continued to hold it through to the reign of
 The same source also makes the same claim about
Tacitus when the Senate acclaimed him emperor in AD 275.
List of known principes senatus