Eumenes III (Aristonikos) was the pretender to the throne of Pergamon.

When the Pergamene king Attalos III died in 134 BC, he bequeathed his kingdom to the Romans. Because the Romans were slow in securing their claim, Aristonikos, son of the earlier Pergamene king Eumenes II, filled the power vacuum, claiming the throne and taking the dynastic name Eumenes. Although unable to capture Pergamon, his revolt lasted four years, until he was defeated and captured by the Romans under the consul M. Perperna. After his surrender, he was paraded through Rome and executed.