The sale "can be carried out in several stages and through a public offering," read the statement from a cabinet meeting authorising the sale of Poste Italiane, which is expected to raise around four billion euros.
The cabinet meeting also approved the sale of Enav, the state air traffic control agency, which could bring around 1.0 billion euros into state coffers.
The government is also planning to list up to 49 percent of state-owned shipbuilder Fincantieri in the biggest privatisations in two decades as part of an effort to reduce Italy's towering debt mountain.
The timing is uncertain and other sales have not been officially approved but they could include a stake of between 4 and 10 percent in the energy major ENI and 13 percent of semiconductor maker STMicroelectronics which is part owned by the French state.
The company Grandi Stazioni, which manages Italy's largest train stations, could also be up for grabs, as could holdings in the gas and electricity grid operators Snam and Terna.
Renzi's two predecessors, Enrico Letta and Mario Monti, had both promised major privatisation programmes as part of an economic reform plan but failed to deliver.
Revenue from privatisations has already been counted in a 2014-2016 economic plan approved by the government last month and Renzi is under pressure to deliver.