On 2 June 1946, Italian people - including, for the first time, all the women - voted to decide whether Italy should keep its old way of being governed or become a 'republic', meaning a country where the people choose their own leaders. The republic won. Every year on the anniversary, Italy celebrates that day of choosing.
The biggest celebration happens in Rome. A long parade marches down a wide street called the Via dei Fori Imperiali, which runs right past the Colosseum. Bands play, flags fly, and people line the road waving the Italian tricolore - the green, white and red flag.
The most spectacular moment is the flyover. Italy's air-force display team - called the Frecce Tricolori, the 'Tricolour Arrows' - flies over Rome in close formation, trailing smoke in green, white and red. Nine jets stream the colours of the flag across the sky. It is a moment many Italian families come outside to watch.
Smaller celebrations happen all over Italy too. Town halls open their doors. Brass bands play in piazzas. Schools in the days before may put on assemblies. Italian flags fly from balconies. Many families eat outside together - because in early June, Italy is usually warm and sunny.