The national sport of a country tends to be one that is linked with the culture of that country. Most European countries have the national sport of football (soccer) and America's national sport is baseball. This is not the most played sport in that country, for example the most played sport in England is football, but cricket is actually our national sport.

A Country can have more than one, for example USA have baseball and American football.Some countries have official, legal national sports. Others simply have unofficial sports that people say are the national sport. For both groups, I would say the criteria are a combination of these factors:

For unofficial sports, current popularity would be a bigger factor than for official sports.
https://sports.stackexchange.com/questions/3686/what-are-criteria-to-define-a-sport-as-national-sport

 Italian football team is the current titleholder. The Italian national soccer team is popularly known by the name of Azzurri for their blue shirts. It is considered to be the second-most successful national football team in the world. Apart from this most of major Italian clubs get the opportunity to compete at a high level of soccer competitions. 

Apart from soccer, water polo is another popular and one of the old Italy sport. The playground used for this game, is a rectangular swimming pool having 18mt breadth. The water should be deep enough. Every team contains 7 players. Among them 1 is goalkeeper, 3 players remain in the defensive position and there are 3 in forward. Players wear blue and black bonnets while the goalkeeper wears a red cap. This sport of water polo lasts for 28 minutes. The players of this sport should be physically strong. Along with it a skilled technical ability is needed. 

Winter sports in Italy are also among the other most watched and enjoyed games. Italy is quite famous for its Winter Olympics. Skiing is probably one of the leisure interests of Italians. On Mount Etna Skiing is found. In 2006 Piemonte of Italy hosted the Winter Olympics. 

 The other recognized sports in Italy include Rugby, Cycling, Basketball, Running Auto racing etc. In recent times the team of rugby consists of 15 players. An oval shaped ball is used for this game. In Italy sports is also quite popular among disabled persons. The sports in Italy carry a great therapeutic value for the disabled Italians. Many physically challenged people are seen to be participating in the sports in Italy.