Buonanno, who was also mayor of the Piedmont town of Borgosesia, was driving towards Varese, in Lombardy, when his car crashed with another, according to Italian media reports.
His wife was on board and hospitalized with injuries.
Buonanno had a track record of pulling offensive stunts. The MEP was suspended and fined in October after wearing a Hitler-style moustache and giving the Nazi salute during a debate at which German Chancellor Angela Merkel was present.
In January 2014 he smeared his face with black greasepaint as he advised Italians to “become a bit darker” if they wanted to be treated as well as black immigrants supposedly are.
And in September 2013 he provoked two openly gay MPs with a fennel bulb, or finocchio, the Italian slang for 'faggot'. The incident happened during a debate about the Italian pasta company Barilla, after its CEO sparked controversy for saying that the company would never feature gay people in its adverts.
He was also suspended from the Italian parliament in April 2014 after waving a fish around to protest the government's immigration policy. He picked out a sea bass to symbolize the food eaten by politicians such as Laura Boldrini, president of the Chamber of Deputies, while arguing that the immigration policy was impoverishing Italians who were forced to eat sardines.
He also said last year that he would give Borgosesia residents a bonus if they bought a gun to “defend themselves from delinquents”.
Tributes were made onTwitter by the Northern League leader, Matteo Salvini, and Marine Le Pen, the leader of France's National.
Un impegno: non molleremo mai, anche per Te.— Matteo Salvini (@matteosalvinimi) June 5, 2016
Ciao Gianluca, mancherai. pic.twitter.com/vRH9xcazTk
But Buonanno's death also triggered some tasteless reactions from Italians. He was "simply an a***hole," wrote one, while another wrote that "death was the only way of getting rid of him".