Seetee Ship is the second of two science fiction novels by Jack Williamson, writing under the pseudonym Will Stewart. It is a fix-up adapting two stories previously published in Astounding Science Fiction magazine, "Minus Sign" (first published in the November 1942 issue) and "Opposites—React!" (two installments in January and February 1943). Seetee Ship was released in 1951 by Gnome Press in an edition of 4,000 copies.