Born Elisa Tia in Grosseto, Tuscany, she moved to Rome with her family. In 1953 was discovered by Roberto Capucci who introduced her to the world of fashion. She became a model and began playing small roles in films. She appeared in Claude Autant-Lara’s Le Rouge et le Noir (1954), but her first important film role came the following year with The Indian Fighter opposite Kirk Douglas, who claimed to have spotted her on a magazine cover and hired her for his production company, Bryna Productions.

In 1956, she won the Silver Bear for Best Actress at the 6th Berlin International Film Festival for playing the title role in Mario Monicelli’s Donatella.

Martinelli was first married to Count Franco Mancinelli Scotti di San Vito, by whom she had a daughter, Cristiana Mancinelli (born 1958), also an actress. In 1968, she married the Paris Match photographer and 1970s furniture designer, Willy Rizzo.

From the mid-1950s through the late 1960s, she divided her time between Europe and the United States, appearing in films such as Four Girls in Town (1957) with Julie Adams, Manuela (1957) with Trevor Howard, Prisoner of the Volga (1959) with John Derek, Hatari! (1962) with John Wayne, The Pigeon That Took Rome (1962) with Charlton Heston, The Trial (1962) directed by Orson Welles, The V.I.P.s (1963) with Elizabeth Taylor and Richard Burton, Rampage (1963) with Robert Mitchum, Woman Times Seven (1967) with Shirley MacLaine, and Candy (1968) with Marlon Brando. From the late 1960s, she worked in Europe in mostly foreign language productions. Her last English language role was as Carla the Agent in Once Upon a Crime (1992) with John Candy. Her final acting appearance was in the 2005 European television series Orgoglio as the Duchessa di Monteforte.

Martinelli died of cancer in Rome on 8 July 2017, at the age of 82.