Senate of the Roman Empire in the context of Lucius Calpurnius Piso the Augur

The Roman Senate (Latin: Senātus Rōmānus) was the highest and constituting assembly of ancient Rome and its aristocracy. With different powers throughout its existence, it lasted from the first days of the city of Rome (traditionally founded in 753 BC) as the Senate of the Roman Kingdom, to the Senate of the Roman Republic and Senate of the Roman Empire and eventually the Byzantine Senate of the Eastern Roman Empire, existing well into the post-classical era and Middle Ages.

During the days of the Roman Kingdom, the Senate was generally little more than an advisory council to the king. However, as Rome was an electoral monarchy, the Senate also elected new Roman kings. The last king of Rome, Lucius Tarquinius Superbus, was overthrown following a coup d'état led by Lucius Junius Brutus, who founded the Roman Republic. During the early Republic, the Senate was politically weak, while the various executive Roman magistrates who appointed the senators for life (or until expulsion by Roman censors) were quite powerful. Since the transition from monarchy to constitutional rule was most likely gradual, it took several generations before the Senate was able to assert itself over the executive magistrates. By the middle Republic, the Senate had reached the apex of its republican power. The late Republic saw a decline in the Senate's power, which began following the reforms of the tribunes Tiberius and Gaius Gracchus. After the transition of the Republic into the Principate, the Senate lost much of its political power as well as its prestige.

The Senate was the governing and advisory assembly of the aristocracy in the ancient Roman Republic. It was not an elected body, but one whose members were appointed by the consuls, and later by the censors, which were appointed by the aristocratic Centuriate Assembly. After a Roman magistrate served his term in office, it usually was followed with automatic appointment to the Senate. According to the Greek historian Polybius, the principal source on the Constitution of the Roman Republic, the Roman Senate was the predominant branch of government. Polybius noted that it was the consuls (the highest-ranking of the regular magistrates) who led the armies and the civil government in Rome, and it was the Roman assemblies which had the ultimate authority over elections, legislation, and criminal trials. However, since the Senate controlled money, administration, and the details of foreign policy, it had the most control over day-to-day life. The power and authority of the Senate derived from precedent, the high caliber and prestige of the senators, and the Senate's unbroken lineage, which dated back to the founding of the Republic in 509 BC. It developed from the Senate of the Roman Kingdom, and became the Senate of the Roman Empire.

Originally the chief magistrates, the consuls, appointed all new senators. They also had the power to remove individuals from the Senate. Around the year 318 BC, the "Ovinian Plebiscite" (plebiscitum Ovinium) gave this power to another Roman magistrate, the censor, who retained this power until the end of the Roman Republic. This law also required the censors to appoint any newly elected magistrate to the Senate. Thus, after this point in time, election to magisterial office resulted in automatic Senate membership. The appointment was for life, although the censor could impeach any senator.

The Roman emperors were the rulers of the Roman Empire from the granting of the name and title Augustus to Octavian by the Roman Senate in 27 BC onward. Augustus maintained a facade of Republican rule, rejecting monarchical titles but calling himself princeps senatus (first man of the Senate) and princeps civitatis (first citizen of the state). The title of Augustus was conferred on his successors to the imperial position, and emperors gradually grew more monarchical and authoritarian.

The style of government instituted by Augustus is called the Principate and continued until the late third or early fourth century. The modern word "emperor" derives from the title imperator, that was granted by an army to a successful general; during the initial phase of the empire, the title was generally used only by the princeps. For example, Augustus's official name was Imperator Caesar Divi Filius Augustus. The territory under command of the emperor had developed under the period of the Roman Republic as it invaded and occupied much of Europe and portions of North Africa and the Middle East. Under the republic, the Senate and People of Rome authorized provincial governors, who answered only to them, to rule regions of the empire. The chief magistrates of the republic were two consuls elected each year; consuls continued to be elected in the imperial period, but their authority was subservient to that of the emperor, who also controlled and determined their election. Often, the emperors themselves, or close family, were selected as consul.

The Temple of Mars Ultor was a sanctuary erected in Ancient Rome by the Roman Emperor Augustus in 2 BCE and dedicated to the god Mars in his guise as avenger. The centerpiece of the Forum of Augustus, it was a peripteral style temple, on the front and sides, but not the rear (sine postico), raised on a platform and lined with eight columns in the Corinthian order style.

According to Suetonius and Ovid, the young Octavian vowed to build a temple to Mars in 42 BCE just before the Battle of Philippi if the god would grant him and Marcus Antonius victory over two of the assassins of Julius Caesar, Gaius Cassius Longinus and Marcus Junius Brutus. However, work did not commence on the temple until after the recovery of the Aquilae in 20 BCE that had been lost by Marcus Licinius Crassus in the disastrous Battle of Carrhae 33 years earlier. Originally, the Roman Senate had decreed that the returned standards were to be housed in a temple to Mars Ultor that was to be built on the Capitoline Hill. Augustus however, declared that he would build it at his own expense on the site of his new forum. Augustus’s decision to wait to fulfill his vow has been speculated to have been due to a reluctance to celebrate his victory over those who were seen as the defenders of Libertas, whereas the return of the standards, and its symbolic revenge against the Parthians, was a more acceptable victory to commemorate.

Lucius Vibius Sabinus was a Roman Senator who lived in the 1st century. His daughter Vibia Sabina married the emperor Hadrian.

Anicius Probus (fl. 525) was a Roman senator living in the Ostrogothic Kingdom who served as the consul of the year 525. He is called "Junior" or "Iunior" in some sources, probably for confusion with Olybrius, a child who served as consul in 491.

He married Proba, daughter of Olybrius and wife Irene, a niece of Eastern Roman Emperor Anastasius I. With her he had a daughter, Juliana, who married Anastasius, son of Anastasius Paulus Probus Sabinianus Pompeius Anastasius, consul in 517, by his marriage to Empress Theodora's illegitimate daughter, whose name has not survived.