Senatorial class

During the Roman Republic, nobilis ("noble," plural nobiles) was a descriptive term of social rank, usually indicating that a member of the family had achieved the consulship. Those who belonged to the hereditary patrician families were noble, but plebeians whose ancestors were consuls were also considered nobiles. The transition to nobilitas thus required the rise of an empire individual, who was considered a "new man" (novus homo). Two of the most famous examples of these self-made "new men" were Gaius Marius, who held the consulship seven times, and Marcus Tullius Cicero.

The Second Samnite War (326–304 BC) was a formative time in the creation of this ruling elite comprising both patricians and plebeians who had risen to power. From the mid-4th century to the early 3rd century BC, several plebeian-patrician "tickets" for the consulship repeated joint terms, suggesting a deliberate political strategy of cooperation.

Scholarly attempts to define nobilitas have led to debates over the particulars of its usage in ancient sources. Fergus Millar points out that nobilis was a descriptive word as used in the Late Republic, and not a technical term for a restricted social group in the sense of peerage. Matthias Gelzer held that the term was reserved for descendants of consuls, and therefore reckoned that Munatius Plancus, consul designate for 42 BC, was the last man to qualify as an ancestor for a nobilis.P.A. Brunt, building on the view of Theodor Mommsen, assembled evidence of broader usage that suggests any curule office might grant the aura of nobilitas. The term is not found in the literature of the mid-Republic, and came into use long after the social and political changes that created "noble" plebeians.

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