The younger Marcus Livius Drusus, son of Marcus Livius Drusus the Elder, was a Roman politician and reformer, most famous as tribune of the plebeians in 91 BC. The failure of his legislative reforms and his subsequent assassination late in 91 BC are often seen as an immediate cause of the Social War (91-88 BC).
M. Livius Drusus' was the son of Marcus Livius Drusus the Elder, a distinguished statesman who had served all the major magistracies of the Cursus honorum as tribune in 122 BC, consul in 112 BC, and censor in 109 BC. Drusus the Elder died in 108 BC, at which point the young Drusus would have become the Pater familias of the Drusi.
Cicero reports that Drusus was a high-minded youth. For example, when serving as Quaestor in Asia Minor, he conspicuously refused to wear his official insignia as a sign of respect.
Drusus was also extremely wealthy after the death of his father. With this wealth, he paid for grand gladiatorial shows during his aedileship: indeed, Drusus was said to have once commented that he spent so much money on other people that he had 'nothing left to give away to anybody but mud and air'. He also built a grand new house on the Palatine Hill, and famously told the architect to build it so that all his fellow-citizens might be able to see to everything he did. This famous house was successively owned by Cicero, Censorinus, and Rutilius Sisenna.
M. Livius Drusus was elected Tribune of the Plebs for 91 BC. Hostile propaganda later portrayed Drusus as a demagogue from the outset of his tribunate, but it is clear from the testimony of Cicero and others that he in fact began with the aim of strengthening senatorial rule and had the backing of the most powerful optimates in the Senate. These included the 'father of the senate' (princeps senatus), Marcus Aemilius Scaurus, who had also served alongside Drusus' father in the censorship of 109 BC; and Lucius Licinius Crassus, the most influential orator of the day.