Fen is a science fiction fanzine by James Kepner.
Published in December 1943 in Los Angeles, California, U.S.A., Fen was an apazine distributed in the26th mailing of the Fantasy Amateur Press Association. It included editorializing by James Kepner and the article "A Study in Protectives" by Carlton J. Fassbeinder.
In December 1943, Kepner also published Toward Yesterday. In 1944, James Kepner released Toward Tomorrow, the follow-up publication to Toward Yesterday. Four issues were released, from Spring 1944 to June 1945.