Virginia Raggi, a member of the populist Five Star Movement (M5S) made the pledge during an address to women mayors from around the world at the Women4Climate conference in Mexico, publishing details on her return to Italy.
"From 2024, the use of diesel cars in the centre of Rome will be banned," she wrote on her Facebook page.
Diesel usage has already been in decline in Europe for several years with carmakers under increasing pressure to return to petrol engines while stepping up the development of electric vehicles.
Two days ago, Britain's Financial Times said Italian-American group Fiat Chrysler plans to ditch diesel from all of its passenger vehicles by 2022 following a huge fall in demand and growing costs.
And on Tuesday, a top German court issued a landmark decision permitting cities to impose diesel driving bans in order to fight pollution, plunging millions of car owners into uncertainty.