Trailer may refer to:
- In transportation
- Trailer (vehicle), an unpowered vehicle pulled by a powered vehicle
- Bicycle trailer, a wheeled frame for hitching to a bicycle to tow cargo or passengers
- Full-trailer
- Semi-trailer
- Travel trailer, or caravan, a type of recreational trailer designed to provide sleeping space
- Construction trailer, temporary accommodation for offices and building materials storage on construction sites
- Semi-trailer truck
- Mobile home, a housing unit built in factories, rather than on site
- Portable classroom, a temporary classroom for schools with insufficient building capacity
- In computing
- Trailer (information technology), data appended to a main block of data to facilitate its processing
- In films and video
- Trailer (book), a short video for marketing a book
- Trailer (film), an advertisement, usually in the form of a brief excerpt or string of excerpts, for a new film
- Teaser trailer, a truncated version of a theatrical or film trailer
- In music
- Trailer (album), a 1994 album from the Northern Irish musical group Ash