Pornographic films (colloquially porn films, pornos, porn), sex films, erotic films, adult films, blue films, sexually explicit films, or 18+ films are films that represent sexually explicit subject matter in order to arouse, fascinate, or satisfy the viewer. Pornographic films represent sexual fantasies and usually include erotically stimulating material such as nudity or fetishes (softcore) and sexual intercourse (hardcore). A distinction is sometimes made between "erotic" and "pornographic" films on the basis that the latter category contains more explicit sexuality, and focuses more on arousal than storytelling; the distinction is highly subjective.

Pornographic films are produced and distributed on a variety of media, depending on the demand and technology available, including traditional film stock footage in various formats, home video, DVDs, mobile devices, Internet pornography, Internet download, or cable TV, in addition to other media. Pornography is often sold or rented on DVD; shown through Internet streaming, specialty channels and pay-per-view on cable and satellite; and viewed in rapidly disappearing adult movie theater. Often due to broadcast or print censorship commissions, general public opinion, public decency laws, or religious pressure groups, overly sexualized content is generally not permitted in mainstream media or on free-to-air television.

Films with risqué content have been produced since the invention of motion pictures in the 1880s. Production of such films was profitable, and a number of producers specialized in their production. Various groups within society considered such depictions immoral, labeled them "pornographic", and attempted to have them suppressed under other obscenity laws, with varying degrees of success. Such films continued to be produced, and could initially only be distributed by underground channels. Because the viewing of such films carried a social stigma, they were viewed at brothels, adult movie theaters, stag parties, home, private clubs, and night cinemas.

In the 1970s, during the Golden Age of Porn, pornographic films were semi-legitimized, to the point where actors not known for appearances in such productions would be cast members (though rarely participating in the explicit scenes); by the 1980s, pornography on home video achieved wider distribution. The rise of the Internet in the late 1990s and early 2000s changed the way pornographic films were distributed, complicating censorship regimes around the world and legal prosecutions of "obscenity".

Pornographic films are typically categorized as either softcore or hardcore pornography. In general, softcore pornography is pornography that does not depict explicit sexual activity, sexual penetration or extreme fetishism. It generally contains nudity or partial nudity in sexually suggestive situations. Hardcore pornography is pornography that depicts penetration or extreme fetish acts, or both. It contains graphic sexual activity and visible penetration. A pornographic work is characterized as hardcore if it has any hardcore content.

Pornographic films are generally classified into subgenres which describe the underlying theme or sexual fantasy which the film and actors attempt to create. Subgenres can also be classified into the characteristics of the performers or the type of sexual activity on which it concentrates and not necessarily on the market to which each subgenre appeals. The subgenres usually conform to certain conventions, and each may appeal to a particular audience.

Production of erotic films commenced almost immediately after the invention of the motion picture.^{[citation needed]} Two of the earliest pioneers were Frenchmen Eugène Pirou and Albert Kirchner. Kirchner, under the name "Léar", directed the earliest surviving erotic film for Pirou. The 7-minute 1896 film Le Coucher de la Mariée had Louise Willy [af; ca; fr; vo] performing a bathroom striptease. Other French filmmakers also considered that profits could be made from this type of risqué films, showing women disrobing.

Also in 1896. Fatima's Coochie-Coochie dance [fr; nl] was released as a short nickelodeon kinetoscope/film featuring a gyrating belly dancer named Fatima. Her gyrating and moving pelvis was censored, one of the earliest films to be censored. At the time, there were numerous risque films that featured exotic dancers. In the same year, The May Irwin Kiss contained the first kiss on film. It was a 47-second film loop, with a close-up of a nuzzling couple followed by a short peck on the lips ("the mysteries of the kiss revealed"). The kissing scene was denounced as shocking and obscene to early moviegoers and caused the Roman Catholic Church to call for censorship and moral reform, because kissing in public at the time could lead to prosecution. Perhaps in defiance and "to spice up a film", this was followed by many kiss imitators, including The Kiss in the Tunnel (1899) and The Kiss (1900). A tableau vivant style was used in short film Birth of The Pearl [cy] (1901) featuring an unnamed long-haired young model wearing a flesh-colored body stocking in a direct frontal pose that provides a provocative view of the female body. The pose is in the style of Botticelli's The Birth of Venus.