A poster is any piece of printed paper designed to be attached to a wall or vertical surface. Typically posters include both textual and graphic elements, although a poster may be either wholly graphical or wholly textual. Posters are designed to be both eye-catching and convey information. Posters may be used for many purposes, and they are a frequent tool of advertisers (particularly of events, musicians and films), and other groups trying to communicate a message.

Posters are also used for reproductions of artwork, particularly famous works, and are generally low-cost compared to original artwork. Another type of poster are educational posters, which may be about a particular subject for educational purposes. Many people also collect posters, and some famous posters have themselves become quite valuable, collectors and vintage posters are usually framed and matted. Posters may be any size.