Hyperbolus was an demagogue during the Peloponnesian war.
who rose to prominence after the death of Cleon in 422 B.C.. He was involved in a three way power struggle in the city, with Nicias and Alcibiades. He hoped to solve this problem by calling an ostracism in 416 B.C.. However, Nicias and Alcibiades allied against him, combigning their supporters, and he was ostracised.
After being ostracised he went to Samos, where he was murdered by oligarchical revolutionaries. Considering his prominence in comic poetry, he must have been quite influential. There is also evidence that he proposed and ammended several well thought out decrees.