Marcus Octavius was a Roman tribune

Tribune

Tribune was a title shared by elected officials in the Roman Republic. Tribunes had the power to convene the Plebeian Council and to act as its president, which also gave them the right to propose legislation before it. They were sacrosanct, in the sense that any assault on their person was...

 and a major rival of Tiberius Gracchus

Tiberius Gracchus

Tiberius Sempronius Gracchus was a Roman Populares politician of the 2nd century BC and brother of Gaius Gracchus. As a plebeian tribune, his reforms of agrarian legislation caused political turmoil in the Republic. These reforms threatened the holdings of rich landowners in Italy...

. A serious and discreet person, he earned himself a reputation as an influential orator. Though originally close friends, Octavius became alarmed by Gracchus's populist agenda and, at the behest of the Roman senate

Roman Senate

The Senate of the Roman Republic was a political institution in the ancient Roman Republic, however, it was not an elected body, but one whose members were appointed by the consuls, and later by the censors. After a magistrate served his term in office, it usually was followed with automatic...

, repeatedly veto

Veto

A veto, Latin for "I forbid", is the power of an officer of the state to unilaterally stop an official action, especially enactment of a piece of legislation...

ed Gracchus' programmes of land reform. Gracchus responded by ultimately having the Plebeian Assembly

Plebs

The plebs was the general body of free land-owning Roman citizens in Ancient Rome. They were distinct from the higher order of the patricians. A member of the plebs was known as a plebeian...

 deprive him of his office and eject him from the Assembly's meeting place in 133 BC. This action led to a serious escalation in the confrontation between the traditionalists and the reformers.

Our primary source for him is Plutarch

Plutarch

Plutarch then named, on his becoming a Roman citizen, Lucius Mestrius Plutarchus , c. 46 – 120 AD, was a Greek historian, biographer, essayist, and Middle Platonist known primarily for his Parallel Lives and Moralia...

's life of Tiberius. According to Plutarch

Plutarch

Plutarch then named, on his becoming a Roman citizen, Lucius Mestrius Plutarchus , c. 46 – 120 AD, was a Greek historian, biographer, essayist, and Middle Platonist known primarily for his Parallel Lives and Moralia...

, Gaius Octavius

Gaius Octavius

Gaius Octavius was an ancestor to the Roman Emperors of the Julio-Claudian dynasty. He was the father of the Emperor Augustus, step-grandfather of the Emperor Tiberius, great-great grandfather of the Emperor Caligula, great-grandfather of the Emperor Claudius, and great-great-great grandfather of...

 was one of his descendants, thus making him an ancestor of Roman Emperor

Roman Emperor

The Roman emperor was the ruler of the Roman State during the imperial period . The Romans had no single term for the office although at any given time, a given title was associated with the emperor...

 Augustus

Augustus

Augustus ;23 September 63 BC – 19 August AD 14) is considered the first emperor of the Roman Empire, which he ruled alone from 27 BC until his death in 14 AD.The dates of his rule are contemporary dates; Augustus lived under two calendars, the Roman Republican until 45 BC, and the Julian...

.