The First Folio is a collection of plays by William Shakespeare, published in 1623 as Mr. William Shakespeare's Comedies, Histories, & Tragedies. The contents of the book were compiled by Shakespeare's friends and colleagues John Heminges and Henry Condell, both actors in the King's Men, the playing company for which Shakespeare wrote. The pair emphasized that the book was meant to replace earlier publications, which they characterised as "stol'n and surreptitious copies, maimed and deformed by frauds and stealths of injurious impostors," asserting that Shakespeare's true words "are now offer'd to your view cured, and perfect of their limbes; and all the rest, absolute in their numbers as he conceived them."

Their publication included thirty-six of Shakespeare's plays. Without it, eighteen of the plays, including Macbeth, Twelfth Night, Julius Caesar, The Tempest, and Measure for Measure, might not have survived.

Facsimile copies of the First Folio are available in print and online, but the age of the original pages along with their uneven printing and rather primitive typesetting make them difficult to read. Setting the First Folio in modern type makes Shakespeare's original works more accessible to modern readers; actually using the First Folio gives modern players and directors a more accurate understanding of how Shakespeare intended the plays to be acted and produced. As Megan Burnett of Bellarmine University writes, "Using a First Folio text can be a most thrilling and rewarding experience for the director, the actors, and the audience. Actors taught to look for and use the clues in a First Folio text are empowered to make fresh and exciting choices for their characters, mentally, vocally and physically, making the performance more entertaining and interesting for the production team, the acting company, and, most importantly, for the audience."