The plan, prompted by the desire of top sides to match the success of England's Premier League after it broke away from the other Football League divisions in 1992, was announced in April and has now been ratified after a meeting of club presidents.
Serie A has slipped behind the Premier League and Spain's La Liga in terms of prestige in recent years and top flight bosses hope going it alone will streamline resources.
The two professional divisions will be run as separate entities having previously been managed together, although Maurizio Beretta, former head of Italy's employers' association, has been appointed as president of Serie A and B.
Club presidents failed to agree, however, on a proposal from the Interior Ministry to introduce special supporter cards which fans would have to carry to enter matches.
The government, trying to stamp out soccer hooliganism in Italy, believes the idea would make it easier to track troublemakers and wants the scheme to start in January.
