The Hydra Club was a social organization of science fiction professionals and fans. It met in New York City during the 1940s and 1950s.
It was founded October 25, 1947 in the apartment of Judith Merril and Frederik Pohl on Grove Street in the Greenwich Village neighborhood of New York. As nine founders were present, the club took its name from the legendary nine-headed monster, the Hydra.
Among its members were Lester del Rey, David A. Kyle, Frederik Pohl, Judith Merril, Martin Greenberg, Robert W. Lowndes, Philip Klass, Jack Gillespie, David Reiner, L. Jerome Stanton, Fletcher and Inga Pratt, Willy Ley, George O. Smith, Basil Davenport, Sam Merwin, Harry Harrison, Jerome Bixby, Groff Conklin, Bea Mahaffey, Murray Leinster, Jack Coggins, and J. Harry Dockweiler.
An article by Merril about the club in the November 1951 Marvel Science Fiction was accompanied by Harry Harrison's drawing caricaturing 41 members. Members caricatured include:
- Lois Miles Gillespie
- H. Beam Piper
- David A. Kyle
- Judith Merril
- Frederik Pohl
- Philip Klass
- Richard Wilson
- Isaac Asimov
- James A. Williams
- Sam Merwin, Jr.
- Martin Greenberg
- Walter I. Bradbury
- Bruce Elliott
- L. Jerome Stanton
- Jerome Bixby
- Basil Davenport
- Robert W. Lowndes
- Olga Ley
- Oswald Train
- Charles Dye
- Frank Belknap Long
- Damon Knight
- Thomas S. Gardner
- Harry Harrison
- Sam Bowne
- Groff Conklin
- Larry T. Shaw
- Lester Del Rey
- Frederic Brown
- Margaret Bertrand
- Evelyn Harrison
- L. Sprague de Camp
- Theodore Sturgeon
- George C. Smith
- Hans Stefan Santesson
- Fletcher Pratt
- Willy Ley
- Katherine MacLean Dye
- Daniel Keyes
- H. L. Gold
- Walter Kubilius
Harrison's caption adds, "The remaining twenty-odd members showed up too late at the meeting."