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's entertainment for the close of the Christmas season. The play centres on the twins Viola and Sebastian, who are separated in a shipwreck. Viola (who is disguised as Cesario) falls in love with 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.

William Shakespeare (bapt. 26 April 1564 – 23 April 1616) was an English playwright, poet, and actor, widely regarded as the greatest writer in the English language and the world's greatest dramatist. He is often called England's national poet and the "Bard of Avon" (or simply "the Bard"). His extant works, including collaborations, consist of some 39 plays, 154 sonnets, three long narrative poems, and a few other verses, some of uncertain authorship. His plays have been translated into every major living language and are performed more often than those of any other playwright. They also continue to be studied and reinterpreted.