Massimiliano Giornetti was born on 29 October 1971 in Carrara, Tuscany. He graduated in English language and literature, then studied fashion design at Polimoda in Florence, with further work at the London College of Fashion and the Fashion Institute of Technology in New York. He began in Rome, working for a year with Anton Giulio Grande on ready-to-wear and couture, and then designed for a cashmere knitwear company.
He joined Salvatore Ferragamo's menswear division in July 2000 and became its creative director in 2004. In January 2010 he took on women's ready-to-wear as well, and within months was named creative director of the whole label, the first person to hold that title at the house. His first women's resort collection was shown in 2011 in Doris Duke's former mansion on Fifth Avenue in New York. For resort 2013 he staged a show in the Louvre's Denon Wing, tied to the company's sponsorship of the Leonardo exhibition Saint Anne, the first time the museum had opened its interior galleries to a fashion show; for spring 2014 he showed at the opening of the Wallis Annenberg Center in Beverly Hills with gowns that recalled the founder's Hollywood years.
Critics praised the polish of his collections, though the New York Times noted in 2016 that his menswear had been faulted for "an excess of correctness". He left Ferragamo in March 2016. He later became creative director of Shanghai Tang in Hong Kong (from 2018) and, in 2021, director of Polimoda, the Florence school where he trained.