Methuselah's Children

Methuselah's Children is a science fiction novel by American writer Robert A. Heinlein. Originally serialized in Astounding Science Fiction in the July, August, and September 1941 issues, it was expanded into a full-length novel in 1958. The novel is part of Heinlein's Future History series of stories. It introduces the Howard families, a fictional group of people who achieved long lifespans through selective breeding.

According to John W. Campbell, the novel was originally to be called While the Evil Days Come Not, a quotation from Ecclesiastes used as a password on the second page of the story.

The novel was the origin of the term "masquerade", now used to refer to a fictional trope of a hidden society within the real world.