In Greek mythology, Iolaus (Greek: ΄Ιόλαος) was a Theban divine hero, son of Iphicles and thus a nephew of Heracles. He often acted as Heracles' charioteer and companion, accompanying him on some of the Twelve Labours.
The Theban gymnasium was named after him, and the Iolaeia, an athletic festival consisting of gymnastic and equestrian events, was held yearly in Thebes in his honor.
Iolaus provided essential help to Heracles in his battle against the Hydra, his second labor. Seeing that Heracles was being overwhelmed by the multi-headed monster, who grew two heads in place of each one cut off, Iolaus sprang to help, cauterizing each neck as Heracles beheaded it.
Upon Heracles' death, Iolaus lit the funeral pyre, though according to some mythographers, this was Philoctetes instead.
- - Pindar, Olympian Ode, VIII, 84
- - Ovid IX, 394.