Quintus Marcius Rex was a consul

Consul

Consul was the highest elected office of the Roman Republic and an appointive office under the Empire. The title was also used in other city states and also revived in modern states, notably in the First French Republic...

 of the Roman Republic

Roman Republic

The Roman Republic was the period of the ancient Roman civilization where the government operated as a republic. It began with the overthrow of the Roman monarchy, traditionally dated around 508 BC, and its replacement by a government headed by two consuls, elected annually by the citizens and...

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He was the grandson of another Quintus Marcius Rex

Quintus Marcius Rex

Quintus Marcius Rex was a member of the Marcii Reges, the family founded by the Roman King Ancus Marcius. His father, praetor in 144 BC, built the Aqua Marcia aqueduct, the longest aqueduct of ancient Rome...

, the consul of 118 BC. He was elected consul for 68 BC with Lucius Caecilius Metellus

Lucius Caecilius Metellus

Lucius Caecilius Metellus was a Roman aristocrat. He was praetor in 71 BC. He succeeded Gaius Verres as governor of Sicily in 70 BC. He died in office as consul in 68 BC. His co-consul was Quintus Marcus Rex.- Family :...

. Caecilius Metellus died near the start of the year and was not replaced. Marcius went to serve in Cilicia as proconsul

Proconsul

A proconsul was a governor of a province in the Roman Republic appointed for one year by the senate. In modern usage, the title has been used for a person from one country ruling another country or bluntly interfering in another country's internal affairs.-Ancient Rome:In the Roman Republic, a...

 and, pressured by his brother-in-law, Publius Clodius, refused to help Lucius Licinius Lucullus

Lucullus

Lucius Licinius Lucullus , was an optimate politician of the late Roman Republic, closely connected with Sulla Felix...

. He gave up his province in 66 BC to comply with the lex Manilia that gave command of the provinces of the east to Gnaeus Pompeius Magnus

Pompey

Gnaeus Pompeius Magnus, also known as Pompey or Pompey the Great , was a military and political leader of the late Roman Republic...

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He was denied a triumph

Roman triumph

The Roman triumph was a civil ceremony and religious rite of ancient Rome, held to publicly celebrate and sanctify the military achievement of an army commander who had won great military successes, or originally and traditionally, one who had successfully completed a foreign war. In Republican...

 upon his return. He was still waiting outside the city for a triumph when the Catilinarian Conspiracy

Catiline

Lucius Sergius Catilina , known in English as Catiline, was a Roman politician of the 1st century BC who is best known for the Catiline conspiracy, an attempt to overthrow the Roman Republic, and in particular the power of the aristocratic Senate.-Family background:Catiline was born in 108 BC to...

 broke out in 63 BC. He was sent to watch the movements of Gaius Manlius, Catilina's general. He refused to listen to Manlius's offers of peace.

Marcius had married the eldest sister of Publius Clodius. He died in 61 without leaving an inheritance to his brother-in-law as he expected.