[4] Hugo Award nominees and winners are chosen by supporting or attending members of the annual World Science Fiction Convention, or Worldcon, and the presentation evening constitutes its central event.

The selection process is defined in the World Science Fiction Society Constitution as instant-runoff voting with six nominees.

Initial nominations of five series each are made by members in January through March, while voting on the ballot of six nominations is performed roughly in April through July, subject to change depending on when that year's Worldcon is held.

Lois McMaster Bujold is the only author to win twice, for the Vorkosigan Saga and World of the Five Gods series.

*   Winners and joint winners Beginning with the 1996 Worldcon, the World Science Fiction Society gave Worldcons the option to award Retrospective Hugo Awards, or "Retro-Hugos", in addition to the regular nominations for the year.