President Sergio Mattarella and other top Italian and Vatican office-bearers will on Thursday attend a ceremony and inaugurate an exhibition in Rome to celebrate the 90th anniversary of the landmark Lateran treaty, the foreign ministry said in a statement.
Thursday's ceremony taking place at Italy's embassy to the Holy See will also mark the 35th anniversary of the concordat - which made changes to the Lateran treaty signed between Italy and the Vatican, the statement added.
Under the 1929 Lateran treaty, the papacy recognized the state of Italy, with Rome as its capital. Italy in return recognized papal sovereignty over the Vatican City.
Catholicism ceased to be Italy's state religion with the 1985 concordat, which modified the 1929 Lateran treaty inked by Italy's late fascist dictator Benito Mussolini and cardinal secretary of state Pietro Gasparri for the papacy.