He had spent the past few days in a Milan hospital as his health deteriorated.
"Our country and the whole world has lost an artist today, who for his whole life fought against the theory of 'the dominant culture is that of the ruling class,' " the statement on his website said.
Fo, who was famed for his sharp political satire and innovative storytelling techniques, was awarded the Nobel Prize in Literature in 1997.
The Nobel Committee described him as someone "who emulates the jesters of the Middle Ages in scourging authority and upholding the dignity of the downtrodden."
The Nobel Prize Twitter feed on Thursday marked Fo's death, news of which came on the same day as this year's winner for literature
-- Bob Dylan -- was announced.
Among Fo's best known works were "Accidental Death of an Anarchist," first performed in 1970, and "Can't Pay? Won't Pay!" from 1974.
He also won renown with the one-man play "Mistero Buffo," an exploration of language, history and local lore that he performed more than 5,000 times worldwide over three decades.
Fo's chief collaborator was his wife, the late actress Franca Rame, with whom he set up the Fo-Rame Company. They first met in 1951 while working on the same theater production in Milan.
According to the Nobel website, Fo told Italian reporters in 1997 that he had never expected to be awarded the Nobel Prize and that the judges had shown courage in giving it to an actor-author for the first time.
He also paid tribute to his wife's contribution, saying he would not have won the prize without her. Besides their first love, theater, the couple also worked on television and movie productions.
Fo, who was also a theater director, was born in 1926 in Italy's northern Lombardy region in a small town by Lake Maggiore.
According to the Nobel website, he learned the art of storytelling from his grandfather, who would tell tales spiced with local news and satire as he traveled the countryside selling produce from a horse-drawn cart.