Ipso Facto was a science fiction fanzine published by The International Speculative Organization in London, England.
Released in April 1961, Ipso Facto was the official organ and the first compilation fanzine of the British apa, The International Publishers Speculative Organisation. It consisted of analytical comments on fantasy apas.
The apa was initiated by John Berry and George Locke in November 1960 and the first issue of Ipso Facto was edited by both men. George Loke was the OE. The second issue and on to the sixth issue were edited by Joe Patrizio and Ted Forsyth. The International Publishers Speculative Organization lasted for three years, with the seventh and final mailing put out in September 1963 by Los Angeles fan Fred Patten.
Contributors were John Berry (Pot Pourri), Bruce Burn, F.M. Busby (Cry of the Nameless), Bill Donaho (Habakkuk, Viper), Ron Ellik (Shangri L'Affaires), Ted Johnstone (Shangri L'Affaires), Robert Lichtman, Ethel Lindsay (Scottishe), George Locke (Smoke), Ed Meskys (Niekas), Norm Metcalf, Len Moffatt (Shangri L'Affaires), Joe Patrizio, Bruce Pelz, Alan Rispin, and Ella Parker (Orion).
Skyrack #33 of June 1961 said, "Quite a line-up!"