WORLDCON

Worldcon — the World Science Fiction Convention — is the principal annual gathering of science fiction fandom. Officially sponsored by the the World Science Fiction Society, it bestows the Hugo Awards.

The Worldcon has been held each year since 1939 (except during World War II, 1942–1945), and moves to a different city each year. While most of the conventions occur in the United States, the event has also been hosted by Australia, Canada, Germany, Japan, Great Britain and the Netherlands.

It is an entirely volunteer-run effort.

from Fancyclopedia 2:

The chief annual gathering of fans is usually designated as an "International Convention."

See Convention.

Worldcon.org
The Long List of Worldcons