The industrial action was called by transport union leader Claudio Claudiani on Wednesday following failed negotiations with the government.
The last major strikes in Italy were in 2005, but national media have called today's measures the most severe in at least 25 years.
Italian rail workers began Friday's strike at 9:00 a.m. local time (8:00 a.m. GMT) and were followed by air, bus and ferry staff.
National airline Alitalia cancelled over 200 domestic and international flights, while rail company Trenitalia cut hundreds of train services, leaving commuters stranded. The industrial action involves around 300,000 workers at cities across the country.
Two days before the main strikes began, taxi drivers in Rome blocked Piazza Venezia in protest against plans to issue several hundred new cab licenses to meet rising demand, causing major traffic jams in the capital.
Neighboring France has been hard-hit by several weeks of transport and energy strikes, the worst in 12 years, sparked by President Nicolas Sarkozy's plans to cut public sector pensions. Pressure on the president has been increased by mass riots in Paris suburbs over the past 5 days.
