Scola died in Rome's polyclinic, where he had been in a coma since Sunday after being admitted to the hospital's cardiac surgery unit.
A leading figure in Italian cinema for more than three decades, Scola directed unforgettable masterpieces featuring Marcello Mastroianni, Sophia Loren, Vittorio Gassman and Nino Manfredi.
His work included "A Special Day," a 1977 Oscar-nominated movie featuring Mastroianni as a persecuted radio journalist and Loren as a sentimental housewife who meet on the day Hitler visited Rome in 1938.
The scene where the two actors move between sheets drying in the sun on the terrace of the apartment block where they are staying is one of the most beautiful scenes in Italian cinema, film critic Francesco Castelnuovo said.
"It still influences young directors," he told the SkyTG24 television channel.
Scola also wrote and directed "We All Loved Each Other So Much," a 1974 comedy-drama about the post-war lives of three partisans fighting for the liberation of Italy.
Tributes swiftly flooded in for the man who, through his films, had so skillfully told the story of Italy over nearly a half century, from the fascist years up to the early 21st century.
Prime Minister Matteo Renzi paid tribute to Scola, saying he was a "master" of the screen, "with an ability that was as incredible as it was razor-sharp in reading Italy, its society and the changes it went through."
Culture Minister Dario Franceschini praised him on Twitter as a "grand master, an extraordinary man, still young until the last day of his life."
Actress Stefania Sandrelli, who starred in one of his greatest films "We All Loved Each Other So Much" in 1974, expressed her sadness at his passing.
"If I had to choose one word out of all, it would be 'us'. He gave me the magic of doing things together and what things we did together, what films!"
Writing on Twitter, actor Alessandro Gassman, son of Vittorio, said "Ciao Ettore, we all loved you so much".
After entering the movie industry as a screenwriter in 1953, Scola got his first chance as director in 1964 with "Let's Talk About Women" - an innovative work of nine vignettes in which Vittorio Gassman plays different characters who seduce women.
He directed 41 films over nearly 40 years, according to the Internet movie database, IMDb.
Paolo Mereghetti, the Corriera della Sera daily's cinema critic, said Scola was a distinctive "political" voice in Italy's postwar cinema.
A former member of the Italian Communist Party, Scola even became minister of culture in a "shadow" cabinet set up by party leaders in 1989.
"He understood where Italy was going, and few cinema directors have that insight," Mereghetti told Sky TG24.