Known for his cutting political satires, including the 1970 farce Accidental Death of an Anarchist, Fo was awarded the Nobel Prize for Literature in 1997.
Announcing his death, Italian Prime Minister Matteo Renzi said: "In Dario Fo, Italy has lost one of the great protagonists of the theatre, of culture, of the civic life of our country.
"His satire, research, his work on set design and his versatile artistic activities are the legacy of one of the world’s great Italians."
Often censored by the Italian government – he was banned by Italian broadcaster Rai for 14 years and refused a visa to the US – Fo caused controversy in 1969 with an improvised retelling of the Christian gospels, Mistero Buffo.
A planned personal appearance at Edinburgh’s Lyceum Theatre – part of a festival celebrating Fo's influence on popular political theatre in Scotland – was cancelled on Sunday. A talk about Dario Fo and political theatre in Scotland takes place at the venue this evening.
David Greig, artistic director of the Lyceum tweeted: "Dario Fo RIP; extraordinary theatre maker, forger a link between theatre, carnival & protest. Scottish theatre owes him a tremendous debt."
Dario Fo RIP; extraordinary theatre maker, forger a link between theatre, carnival & protest. Scottish theatre owes him a tremendous debt.
— David Greig (@DavieGreig) October 13, 2016
RIP Dario Fo.
What a man. What a voice.
— Stephen Unwin (@RoseUnwin) October 13, 2016
RIP Dario Fo. Great playwright, brilliant political satirist, true humanist.
— Michael Mayer (@MichaelMayerDIR) October 13, 2016
Sad to hear of the death of theatrical revolutionary Dario Fo. Challenged authority throughout his entire career, something to aspire to RIP
— David Mercatali (@DavidMercatali) October 13, 2016