Screenwriting or scriptwriting is the art and craft of writing scripts for mass media such as feature films, television productions or video games. It is often a freelance profession.

Screenwriters are responsible for researching the story, developing the narrative, writing the script, screenplay, dialogues and delivering it, in the required format, to development executives. Screenwriters therefore have great influence over the creative direction and emotional impact of the screenplay and, arguably, of the finished film.

Screenwriters either pitch original ideas to producers, in the hope that they will be optioned or sold; or are commissioned by a producer to create a screenplay from a concept, true story, existing screen work or literary work, such as a novel, poem, play, comic book, or short story.

The act of screenwriting takes many forms across the entertainment industry. Often, multiple writers work on the same script at different stages of development with different tasks. Over the course of a successful career, a screenwriter might be hired to write in a wide variety of roles.

Some of the most common forms of screenwriting jobs include:

Spec scripts are feature film or television show scripts written without the commission of, but is on speculation of sale to a film studio, production company, or TV network. The content is usually invented solely by the screenwriter, however spec screenplays can also be based on established works or real people and events. The spec script is a Hollywood sales tool with the vast majority of scripts written each year being spec scripts, but only a small percentage make it to the screen. Though a spec script is usually a wholly original work, it can also be an adaptation.

In television writing, a spec script is a sample teleplay written to demonstrate the writer's knowledge of a show and ability to imitate its style and conventions. It is submitted to the show's producers in hopes of being hired to write future episodes of the show. Budding screenwriters attempting to break into the business generally begin by writing one or more spec scripts.

Although writing spec scripts is part of any writer's career, the Writers Guild of America forbids members to write "on speculation". The distinction is that a spec script is written as a sample independently by the writer; what is forbidden is writing a script for a specific producer without a contract. In addition to writing a script on speculation, it is generally not advised to write camera angles or other directional terminology, as these are likely to be ignored. A director may write up a shooting script themselves, a script that guides the team in what to do in order to carry out the director's vision of how the script should look. The director may ask the original writer to co-write it with them or to rewrite a script that satisfies both the director and producer of the film/TV show.