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 with a cover drawn by James V. Taurasi. It featured a story by Gertrude Kuslan entitled "An Adventure In Time", and a fiction piece by Taurasi called "It Happened On Pluto". Taurasi had been the founder and editor of Cosmic Tales from 1937 till 1938, at which time he handed the fanzine over to the Kuslans to edit.
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.