Olivier Martinez was born in Paris, France to a working-class family. His father was a Spanish professional boxer born in Spanish Morocco and his mother was a French secretary. He studied at the prestigious CNSAD and began his acting career in his native France in 1990, and quickly achieved a relative success. Martinez was raised Roman Catholic.

In 1994, Martinez won a César Award as "Most Promising Actor" for his role in Un, deux, trois, soleil (1993). This was followed by a leading role in Jean-Paul Rappeneau period film The Horseman on the Roof (Le Hussard sur le Toit) in 1995 in which he starred alongside Juliette Binoche as an Italian nobleman. The film was hailed as the most expensive French film at that time in history but failed to reach its $35 million budget.
In 1996/7 he appeared in Bertrand Blier's romantic comedy My Man (Mon Homme) alongside Anouk Grinberg, Gérard Lanvin, and Valeria Bruni Tedeschi.
Later in 1997 he played a leading role in Bigas Luna's drama The Chambermaid on the Titanic (La Femme de chambre du Titanic) alongside Romane Bohringer, set during the time of the Titanic's sinking voyage in 1912. Martinex portrays a French foundry worker who wins a strongman contest and the its prize of a trip to Southampton to see the launch of the Titanic. The film was well-received; Mick LaSelle of the San Francisco Chronicle praised what he felt was a rare honest portrayal of male sexuality by Martinez.

Martinez first came to mainstream attention in Hollywood films with his performance in Julian Schnabel's Before Night Falls (2000) opposite Javier Bardem and Johnny Depp. The screenplay is based on the autobiography of the same name of Reinaldo Arenas, which was published in English in 1993. The film was highly critically acclaimed, although Martinez's performance was overshadowed by that of Bardem in the eyes of critics. He was later noted for his performance opposite Diane Lane in Unfaithful (2002)