The action film is a film genre that predominantly features chase sequences, fights, shootouts, explosions, and stunt work. The specifics of what constitutes an action film has been in scholarly debate since the 1980s. While some scholars such as David Bordwell suggested they were films that favor spectacle to storytelling, others such as Geoff King stated they allow the scenes of spectacle to be attuned to storytelling. Action films are often hybrid with other genres, mixing into various forms such as comedies, science fiction films, and horror films.

While the term "action film" or "action adventure film" has been used as early as the 1910s, the contemporary definition usually refers to a film that came with the arrival of New Hollywood and the rise of anti-heroes appearing in American films of the late 1960s and 1970s drawing from war films, crime films and Westerns. These genres were followed by what is referred to as the "classical period" in the 1980s. This was followed by the post-classical era where American action films were influenced by Hong Kong action cinema and the growing using of computer generated imagery in film. Following the September 11 attacks, a return to the early forms of the genre appeared in the wake of Kill Bill and The Expendables films.

Scott Higgins wrote in 2008 in Cinema Journal that action films are both one of the most popular and popularly derided of contemporary cinema genres, stating that "in mainstream discourse, the genre is regularly lambasted for favoring spectacle over finely tuned narrative." Bordwell echoed this in his book, The Way Hollywood Tells It, writing that the reception to the genre as being "the emblem of what Hollywood does worst."

In the Journal of Film and Video, Lennart Soberson stated that the action film genre has been a subject of scholarly debate since the 1980s. Soberson wrote that repeated traits of the genre include chase sequences, fights, shootouts, explosions, and stunt work while other scholars asserted there were more underlying traits that define the genre. David Bordwell in The Way Hollywood Tells It wrote that audiences are "told that spectacle overrides narrative" in action cinema while Wheeler Winston Dixon echoed that these films were typified by "excessive spectacle" as a "desperate attempt to mask the lack of content." Geoff King argued that the spectacle can also be a vehicle for narrative, opposed to interfering with it. Soberson stated that Harvey O'Brien had "perhaps the most convincing understanding of the genre", stating that the action film was "best understood as a fusion of form and content. It represents the idea and ethic of action through a form in which action, agitation and movement are paramount."

O'Brien wrote further in his book Action Movies: The Cinema of Striking Back to suggest action films being unique and not just a series of action sequences, stating that that was the difference between Raiders of the Lost Ark (1981) and Die Hard (1988), that while both were mainstream Hollywood blockbusters with a hero asserting masculinity and overcoming obstacles to a personal and social solution, John McClane in Die Hard repeatedly firing his automatic pistol while swinging from a high rise was not congruent with the image of Indiana Jones in Raiders swinging his whip to fend off villains in the backstreets of Cairo. British author and academic Yvonne Tasker expanded on this topic, stating that action films have no clear and constant iconography or settings. In her book The Hollywood Action and Adventure Film (2015), she found that the most broadly consistent themes tend to be a characters quest from freedom from oppression such as a hero overcoming enemies or obstacles and physical conflicts or challenge, usually battling other humans or alien opponents.

By late 2010s studies of genre analysis, the term "genre" itself is often replaced or supplemented with the words "mode" and "narrative form" with all three terms often being used interchangeably. Johan Höglund and Agnieszka Soltysik Monnet said that the difference between these concepts are elusive, but stated that genre could be defined as belonging to specific historical and cultural moments while "mode" and "form" can refer to a larger pattern that operates across a wider historical and cultural field. In their book Action Cinema Since 2000 (2024), Tasker, Lisa Purse, and Chris Holmlund stated that thinking of action as a mode is more helpful than thinking of it as a genre. The three authors suggested that action frames a certain manner of filmmaking and viewing exceed genre without eclipsing it stating that websites such as IMDb and Wikipedia rarely label films by a single genre and that streaming services such as Amazon Prime and Netflix similarly dilutes what is marketed and received as action.

In transnational cinema, there are two major trends in action films: Hollywood action films and their style being imitated around the globe and the other being Chinese-language martial arts films. The roots of action films extend into the beginning of film but it was only in the mid-20th century when action films developed into their own recognizable genre instead of being a collection of other types of films such as Westerns, swashbucklers or adventure films. Films have been described "action films" or "action-adventure film" as early as the 1910s. Only by the 1980s was the term action as its own unique genre used routinely in terms of promotion and reviewing practices.

The first Chinese-language martial arts films can be traced to Shanghai cinema of the late 1920s. These films were popular during the period, which comprised almost 60% of the total Chinese films. Man-Fung Yip stated that these film were "rather tame" by contemporary standards. He wrote that they lacked the kind of dazzling action choreography as expected today and had crude and rudimentary special effects. These films came under increasing attack by both government officials and cultural elites for their allegedly superstitious and anarchistic tendencies, leading them to be banned in 1932. It was not until the base of Chinese commercial filmmaking was relocated from Shanghai to Hong Kong in the late 1940s that martial arts cinema was revived. These films contained much of the characteristics of the previous era. During this period, over 100 films were based on the adventures of real life Cantonese folk hero Wong Fei-hung who first appeared in film in 1949. These films primarily on circuited within Hong Kong and Cantonese-speaking areas with Chinese diaspora. Yip continued that these Hong Kong films were still lagging behind in aesthetic and technical standards that films from the United States, Europe and Japan had during this period.