Marcello Cesare Augusto Petacci (Italian pronunciation: [marˈtʃɛllo ˈtʃeːzare auˈɡusto peˈtattʃi]; Rome, 1 May 1910 – Dongo, Lombardy, 28 April 1945) was an Italian surgeon and businessman, the brother of actress Maria Petacci and of dictator Benito Mussolini's lover Clara Petacci.
Accused by many of enriching himself illegally through his closeness to Mussolini, Petacci managed in the last days of the Second World War to escape to Switzerland with his family, but chose to go back to Italy. He was captured and executed a few days later by partisans along Lake Como at the same time as Mussolini and his sister Clara.