Ergo Sum was a science fiction fanzine published by Paul Wyskowski.
Ergo Sum was published in the 1970s in Ottawa, Ontario, Canada. It had previously been named Differential, and under that name 37 issues had been published, from September 1962 till August 1965, After a break the editor began publishing again, with the new name but retaining the same numbering of issues, so that the first issue of Ergo Sum was #38.
The fanzine featured fiction, news, and commentary. Also included were two pages of poetry, with Contributions coming from E.E. Evers and Paul Wyskowski.