Ipso Facto was a science fiction fanzine published by Ted Forsth and Joe Patrizio in London, England.
Released in April 1961, Ipso Facto was the first compilation zine of the British apa, The International Publishers Speculative Organisation. It consisted of analytical comments on fantasy apas. Contributors were John Berry (Pot Pourri), F.M. Busby (Cry of the Nameless), Bill Donaho (Habakkuk, Viper), Ron Ellik (Shangri L'Affaires), Lichtman, Ethel Lindsay, George Locke (Smoke), Ed Meskys (Niekas), Metcalf, Len Moffatt (Shangri L'Affaires), Joe Patrizio, Bruce Pelz, Alan Rispin, Ted Johnstone (Shangri L'Affaires), Meskys and Ella Parker (Orion).
Skyrack #33 of June 1961 said, "Quite a line-up!"