Dario Fo (born 24 March 1926) is an Italian actor-playwright, theater director, stage designer, songwriter and political campaigner, and recipient of the 1997 Nobel Prize in Literature. "Arguably the most widely performed contemporary playwright in world theatre," much of his dramatic work depends on improvisation and comprises the recovery of "illegitimate" forms of theater, such as those performed by giullari (medieval strolling players) and, more famously, the ancient Italian style of commedia dell'arte.

His plays have been translated into 30 languages and performed across the world, including in Argentina, Chile, England, Holland, Poland, Romania, South Africa, South Korea, Spain, Sweden, and Yugoslavia. His work of the 1960s, 1970s and 1980s is peppered with criticisms of assassinations, corruption, organised crime, racism, Roman Catholic theology and war. Throughout the 1990s and 2000s, he took to lampooning Forza Italia and its leader Silvio Berlusconi, while his targets of the 2010s have included the banks amid the European sovereign-debt crisis.

Fo's solo pièce célèbre, titled Mistero Buffo and performed across Europe, Canada and Latin America over a 30-year period, is recognised as one of the most controversial and popular spectacles in postwar European theatre and has been denounced by the Vatican as "the most blasphemous show in the history of television." The title of the original English translation of Non Si Paga! Non Si Paga! (Can't Pay? Won't Pay!) has passed into the English language.

His receipt of the 1997 Nobel Prize in Literature marked the "international acknowledgment of Fo as a major figure in twentieth-century world theatre." The Swedish Academy praised Fo as a writer "who emulates the jesters of the Middle Ages in scourging authority and upholding the dignity of the downtrodden." He currently owns and operates a theatre company with his wife, actress Franca Rame, with whom he lives in Milan.