<p>Failure to launch (FTL) is a phrase used to describe abled young adults who live with their parents, are not in school, and are not employed, reflecting difficulties in adult functioning and delayed achievement of expected developmental milestones. Although frequently encountered in clinical settings from parents seeking treatment for their children and themselves, FTL has received little systematic empirical attention in the clinical psychology literature. The present review disentangles FTL from related constructs and highlights the need for a dedicated body of research. First, we define FTL and review findings from one empirical study of FTL adults. Next, we compare FTL to neighboring constructs such as peter-pan syndrome, pathological demand avoidance, “not in education, employment, or training” (NEET), boomerang children, modern-type depression, and hikikomori, emphasizing both points of overlap and distinction. We then review relevant findings from these literatures, including discussion of prevalence rates, correlates, risk factors, and outcomes of related syndromes, with a particular focus on the hikikomori literature. Next, we review existing assessment tools and summarize emerging psychotherapeutic interventions. We conclude by considering how researchers can draw on existing literature to inform future research on FTL youth. Although FTL appears to be a pressing clinical problem, research is necessary to understand its etiology and developmental course and to identify avenues for prevention and intervention.</p>