The Nucleus is a science fiction fanzine by Gertrude Kuslan and Louis Kuslan.
Gertrude and Louis Kuslan published eleven issues of The Nucleus in the 1930s and 1940s in West Haven, Connecticut, U.S.A. The first issue appeared in July of 1938. The last issue was released in 1944.
Vol. 3 No. 3 appeared in 1942. It included social commentary, and "Portrait of a Fan", a spoof of Forrest Ackerman by Gertrude Kuslan.