Gaius Blossius (2nd century BCE) is, according to Plutarch, a philosopher and student of the Stoic philosopher Antipater of Tarsus, from the city of Cumae in Campania, Italy, who (along with the Greek rhetorician, Diophanes) instigated Roman tribune Tiberius Gracchus to pursue a land reform movement on behalf of the plebs.

Tiberius is accused by his political opponents of attempting to provoke a popular uprising, and have himself crowned King.

Eventually, he is assassinated, and his body thrown into the river Tiber.