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. It was called a "Cosmic Publication" and it was distributed through the Fantasy Amateur Press Association. The first issue appeared in July of 1938. It featured a fiction story by Gertrude Kuslan entitled "An Adventure In Time", and a story called "It Happened On Pluto", by James V. Taurasi, who was editor of Cosmic Tales, which as of 1938 was edited by the Kuslans. The cover featured a drawing by Taurasi.
Vol. 3 No. 3 appeared in 1942. It included social commentary, and "Portrait of a Fan", a spoof of Forrest Ackerman ( editor of Voice of the Imagi-Nation) by Gertrude Kuslan.
The last issue was released in 1944.