The Comedy of Twelfth Night is a classic play by William Shakespeare, first performed in 1602. It tells the story of Viola, a young woman who is shipwrecked on the coast of Illyria and disguises herself as a man in order to gain employment in the court
From Wikipedia
Twelfth Night, or What You Will is a romantic comedy by William Shakespeare, believed to have been written around 1601–1602 as a Twelfth Night entertainment for the close of the Christmas season. The play centres on the twins Viola and Sebastian, who are separated in a shipwreck. Viola falls in love with the Duke Orsino, who in turn is in love with Countess Olivia. Upon meeting Viola, Countess Olivia falls in love with her, thinking she is a man.