Pentheus was the second (or possibly third) king of Thebes. He was the son of Echion and Cadmus' daughter, Agave. He came to a fearful end. He was spotted hiding in a tree by Agave and her sisters, where he was trying to spy on the women in their bacchic (or dionysiac) revels.
In their madness, the women assumed he was a wild beast, so pulled him down and tore him to pieces. This was the revenge of Dionysus on Pentheus, who had refused to honour Dionysus and had attempted to ban such revels. Since he was doomed to this fate at the hands of Dionysus, Pentheus can thus be regarded as a 'man of woe' and his name interpreted as 'grief (penthos).