Joséphine de Beauharnais was the first wife of Napoléon I, which made her the first Empress of the French.

Actually, her marriage to Napoleon I wasn't her first; she was married to Alexandre de Beauharnais, who was guillotined during the Reign of Terror, and she herself was imprisoned in the Carmes prison until five days after Alexandre's execution. Joséphine had affairs with several French politicians, later becoming Napoléon's mistress. They got married about a year after their first meeting.

More Info: en.wikipedia.org