Cosplay is a term that is short for "costume play," and it started out as a Japanese subculture that centered on dressing up as characters from manga, anime, and video games. However, in some circles, the meaning of cosplay has been expanded to simply mean "wearing a costume." Cosplayers in Japan often refer to themselves as reyazu.

In Japan, cosplay can be seen at video game shows, as well as at costume parties at nightclubs and amusement parks. Also, some Japanese teenagers gather with like-minded youths in areas such as Tokyo's Harajuku district to engage in cosplay. There are also a number of cosplay cafes in Tokyo's Akihabara district, where waitresses dress up as game or anime characters. The single largest event for cosplay in Japan is Comiket. The event, which is held in the summer and winter, attracts many cosplayers and manga otaku, who meet on the roof of an exhibition center.

In America, cosplay is primarily seen at anime, video game, and science fiction conventions. Many anime conventions include cosplay contests. Usually, the contest is a test of skill, design, and audience reaction. Contestants are judged either before hand or on stage during the actual competition. These contests have led to the formation of cosplay groups that usually plan for conventions months in advance. The increased popularity of cosplay has brought about the addition of other cosplay-based events at anime conventions, such as the Anime Dating Game and Cosplay Human Chess.

In Japan, there are two magazines devoted to cosplay: COSMODE and Dengeki Layers. There are also two emerging cosplay magazines outside of Japan: AniCoz (which is published in the United States) and Cosplaymix (which is published in Mexico).

Cosplay costumes are very different from what many people think of as typical Halloween costumes. Since cosplay requires someone to literally become a character, the intricate details of the costume become extremely important; the costumes must completely adhere to the designs of the character's outfit and look. Some cosplayers go so far as to make sure the seams are aligned properly, that the thread colors are appropriate, and that the fabric colors precisely match the character's attire.

One issue that arises when cosplaying as anime characters is the fact that the characters generally have bodily proportions that cannot be easily mimicked by many typical cosplayers. There has been debate between cosplay fans about how important this element may or may not be when cosplaying.