Marco Formentini (born 3 July 1970 in Lavagna, Genova) is a male freestyle swimmer from Italy. He also competes in the open water swimming, winning a silver and a bronze medal at the World Aquatics Championships.
Formentini competed for his native country at the 1996 Summer Olympics in Atlanta, Georgia, finishing in 18th place in the men's 1500 m freestyle event. He was affiliated with Gruppo Sportivo Carabinieri and Rari Nantes Savona in the 1990s.