Rhesus (, Rhesos) is an Athenian tragedy that belongs to the transmitted plays of Euripides. Its authorship has been disputed since antiquity, and the issue has invested modern scholarship since the 17th century when the play's authenticity was challenged, first by Joseph Scaliger and subsequently by others, partly on aesthetic grounds and partly on peculiarities in the play's vocabulary, style and technique. The conventional attribution to Euripides remains controversial.