La Tosca is a five-act drama by the 19th-century French playwright Victorien Sardou. It was first performed on 24 November 1887 at the Théâtre de la Porte Saint-Martin in Paris, with Sarah Bernhardt in the title role. Despite negative reviews from the Paris critics at the opening night, it became one of Sardou's most successful plays and was toured by Bernhardt throughout the world in the years following its premiere. The play itself had dropped from the standard theatrical repertoire by the mid-1920s, but its operatic adaptation, Giacomo Puccini's Tosca, has achieved enduring popularity. There have been several other adaptations of the play including two for the Japanese theatre and an English burlesque, Tra-La-La Tosca as well as several film versions.

Victorien Sardou was a French dramatist. He is best remembered today for his development, along with Eugène Scribe, of the well-made play. He also wrote several plays that were made into popular 19th-century operas such as La Tosca (1887) on which Giacomo Puccini's opera Tosca (1900) is based, and Fédora (1882) and Madame Sans-Gêne (1893) that provided the subjects for the lyrical dramas Fedora (1898) and Madame Sans-Gêne (1915) by Umberto Giordano. His play Gismonda, from 1894, was also adapted into an opera of the same name by Henry Février.