(Latin: respectively, “Best Ones,” or “Aristocrats”, and “Demagogues,” or “Populists”), two principal patrician political groups during the later Roman Republic (ancient Rome) from about 133 to 27 BC. The members of both groups belonged to the wealthier classes.

The Optimates were the dominant group in the Senate. They blocked the wishes of the others, who were thus forced to seek tribunician support for their measures in the tribal assembly and hence were labeled Populares, “demagogues,” by their opponents. The two groups differed, therefore, chiefly in their methods: the Optimates tried to uphold the oligarchy; the Populares sought popular support against the dominant oligarchy, either in the interests of the people themselves or in furtherance of their own personal ambitions. Finally, it is well to remember that the Senate's authority was based on custom and consent rather than upon law. It had no legal control over the people or magistrates: it gave, but could not enforce, advice. Until 133 BC any challenge to its authority was little more than a pinprick, but thereafter more deadly blows were struck, first by such Populares as Tiberius and Gaius Gracchus, then by Gaius Marius, and finally by the army commanders from the provinces.