Hegelochus (Ancient Greek: Ἡγέλοχος, fl. 408 BC) was an Ancient Greek actor active in Athens in the 5th century BC, best remembered for a slight pronunciation mistake that derailed his career.
Hegelochus acted in the play Orestes by Euripides when it was performed in the City Dionysia dramatic festival in 408 BC. He was playing the title role of Orestes. In line 279 of the play, instead of "after the storm I see again a calm sea" (γαλήν' ὁρῶ, galḗn' horô), Hegelochus recited "after the storm I see again a weasel" (γαλῆν ὁρῶ, galên horô). 
Hegelochus' mistake was to use a rising-falling tone instead of a rising tone. In the nominative, the adjective forms that give "calm sea" are γαληνός, γαληνόν (galēnós, galēnón), and "weasel" is either γαλῆ or γαλέη (galê, galéē). The accusative plural of γαληνόν is γαληνά (galēná), which, after apocope, results in "γαλήν' ὁρῶ"; the accusative of γαλῆ is γαλῆν (galên)." This can be explained by his running out of breath and failing to make the elision. Moreover, the weasel was an unlucky animal, contrasting with the optimistic intent of the line.
This error was widely mocked, Hegelochus was ruined, and he never acted again. It may also have contributed to Euripides leaving Athens.
The error was mocked by Sannyrion in his Danae, in Aristophanes' The Frogs, by the comic poet Plato, and by Strattis in his The Human Orestes (Ἀνθρωπορραιστής), Kinesias (Κινησίας), and Psychastae (Ψυχασταί).