The action of the comedy takes place in a fictional country – Illyria. The ruler of Illyria, Duke Orsino, is in love with Countess Olivia. Countess in mourning for her brother’s death.
The twins, brother and sister Sebastian and Viola, suffered a shipwreck, ended up in Illyria and lost each other. Viola disguised in men’s clothing, appears at the court of Orsino. The duke fell in love with a young man named Caesario (this name was taken by Viola), and he brought her closer to him. Viola falls in love with the duke. Orsino does not notice this and gives his new page instructions to go to Olivia and try to woo her.
At Olivia’s court lives her uncle Sir Toby, a drunkard and merrymaker. He spends time together with Sir Andrew, who is also unsuccessfully seeking Olivia’s attention. Caesario seeks an audience with Olivia and gives her the news from Orsino. It ends abruptly: Olivia politely pays homage to the duke’s virtues, but falls in love at first sight with his messenger.
In the city, meanwhile, appears Sebastian, mourning his sister, believing that she died. A series of misunderstandings begins. Brother and sister, extremely similar to each other, are all confused. In the finale of the play, Sebastian marries Olivia, and Viola, admitting that she is a girl – with Orsino. The brawler Sir Toby is punished, the pedantic housekeeper Malvolio is ridiculed.
The play was probably completed by Shakespeare between 1600 and 1601. The main male role, Orsino, was probably suggested by Virginio Orsini (1572-1615), Duke of Brač, an Italian aristocrat who visited London in the winter of 1600-1601. The play was not published until it was included in Shakespeare’s First Folio in 1623.