Jean-Paul Sartre directly addresses some of the core issues involved in the contemporary debate about the desirability of immortality. He thinks mortality can never be the source of life’s meaning because death cuts us off before meaning can be determined, and because any meaning that survives is no longer our own. These claims already put Sartre at odds with immortality naysayers who believe the limitations provided by our chronological finitude are essential to meaning, but he takes it further by arguing that the actual meaning-generating limitations of our temporal situation would remain intact even if our lives never ended. Thus, Sartre seems like an obvious resource for anyone defending immortality. However, he does suggest one major reason to be wary. The possibility of ending up in a perpetually miserable situation makes truly indestructible immortality less attractive, and this diminished attractiveness suggests that we should not take the ability to die too lightly. With all of this in mind, this chapter argues for a form of immortality involving indefinite life extension with the possibility to opt out in case existence becomes irreparably intolerable.