Publius Valerius Poplicola or Publicola (d. 503 BC) was one of four Roman aristocrats who led the overthrow of the monarchy, and became a Roman consul, the colleague of Lucius Junius Brutus in 509 BC, traditionally considered the first year of the Roman Republic. The authors of America's The Federalist Papers used the pseudonym "Publius" in his honour.
According to Livy and Plutarch, the Valerii were of Sabine origin, but settled in Rome during the reign of Titus Tatius, a contemporary of Romulus, and worked for the peaceful unification of both peoples.
Valerius came from a wealthy family. His father was Volesus Valerius, and his brothers were Marcus Valerius Volusus and Manius Valerius Volusus Maximus. He had a daughter, Valeria. Before holding public office, Valerius had spoken in defense of the plebs, the common people of Rome.
In 509 BC, Valerius was one of the leaders of the Roman revolution, together with Lucius Junius Brutus, Lucius Tarquinius Collatinus, and Spurius Lucretius Tricipitinus. Winning over public opinion while the king was campaigning away from the city, they deposed and banished Lucius Tarquinius Superbus, the seventh and last King of Rome. In place of the monarchy, they established a republic, together with the office of consul. Brutus and Collatinus were elected the first consuls.