Fans of science fiction, anime, manga, and more have been dressing in costume for a long time, and nobody seems to know exactly when this activity began. Even as far back as 1939, a fan of science fiction named Forrest J. Ackerman dressed in a "futuristic costume" at the 1st World Science Fiction Convention:

However, the hobby was not called cosplay until 1984. A Japanese man named Nobuyuki Takahashi created the word "cosplay"  by combining the English words "costume" and "play" while he was attending the 1984 Los Angeles Science Fiction Worldcon convention. He was impressed by all of the costumes he saw there, and began writing about "cosplay" in Japanese magazines, such as the one shown below:

In modern times, cosplay is seen as a primarily Japanese hobby with some Western "copycats," but it is interesting to see that the hobby seemed to develop at the same time in multiple countries! No one country can claim to be the place where cosplay began, although Japanese fans of the hobby are well known worldwide for their excellent costumes and enthusiasm for cosplay.