A teaser trailer, or teaser is a short trailer used to advertise an upcoming movie, game or television series.

Teasers, unlike typical theatrical trailers, are usually very short in length (between 30–60 seconds) and usually contain little if any actual footage from the film. Sometimes it is merely a truncated version of a theatrical trailer. They are usually released long in advance of the film they advertise. One of the reasons for the name "teaser" is because they are shown usually a long time (one or one and a half years) before the movie comes out, so as to "tease" the audience.

Teasers are also commonly used in advertising. The so-called teaser ad/campaign consists typically in (a series of) small, cryptic, challenging, advertisements which anticipate a large(r), full-blown campaign for a product launch or otherwise important event.

Teaser trailers are usually only made for big-budget and popularly themed movies. Their purpose is less to tell the audience about a movie's content than simply to let them know that the movie is coming up in the near future, and to add to the hype of the upcoming release. Teaser trailers are often made while the film is still in production or being edited and as a result they may feature scenes or alternate versions of scenes that are not in the finished film. Other ones (notable Pixar films) have scenes made for use in the trailer only. Teaser trailers today are increasingly focused on internet downloading and the convention circuit.

An early example of the teaser trailer was the one for the Superman film by Richard Donner. The film was already nearly a year late; it was designed to re-invigorate interest in the release. The teaser for the Batman film starring Michael Keaton in 1989 was an emergency marketing move that successfully convinced angered comic book fans that the film would respect the source material.Fact: date=February 2007

Recent examples of major motion picture events that used teaser trailers to gain hype are the Lord of the Rings trilogy, the Disney/Pixar film Cars, the newer Star Wars films and the Spider-Man films. The Da Vinci Code teaser trailer was released before a single frame of the movie had been shot.Fact: date=August 2007 Harry Potter and the Half-Blood Prince's teaser trailer was released surprisingly late, but when it was pushed back from November 21, 2008 to July 17, 2009, the trailer was surprisingly early.

Some teasers have appeared over a year (or longer) prior to the movie's release date. (For example, a teaser for The Incredibles was attached to the May 2003 film Finding Nemo, a full 18 months before The Incredibles was released, a teaser for Ben 10 Alien Force the Movie was released during the premiere of Star Wars: The Clone Wars about 13 months early, and The Princess and the Frog being shown on the internet since August 4, 2008, 14 months before the movie's premiere..)