In “Twelfth Night,” Viola adopts the name Cesario when she disguises herself as a man. Shipwrecked on the coast of Illyria and separated from her twin brother Sebastian, Viola believes she must protect herself in an unfamiliar country. With help from a sea captain, she disguises herself as a young man and enters the service of Duke Orsino.
As Cesario, Viola becomes Orsino’s page and trusted messenger. Orsino sends Cesario to court Countess Olivia, who has rejected the duke’s advances while mourning her brother. The disguise creates the play’s central romantic complication: Viola loves Orsino, Orsino loves Olivia, and Olivia falls in love with Cesario, whom she believes is a man.
Cesario is not Viola’s only disguise-related name in Shakespeare. The name reflects her temporary male identity, while the mistaken-identity plot depends on her close resemblance to Sebastian. When Sebastian appears in Illyria, characters repeatedly confuse the twins, until their reunion finally exposes the truth and allows Viola to marry Orsino.
The play was probably written around 1601–1602 and was first published in the 1623 First Folio. Its gender confusion was especially theatrical because Elizabethan women’s roles were performed by boys or young men.