In popular psychology, a quarter-life crisis is an existential crisis involving anxiety and sorrow over the direction and quality of one's life which is most commonly experienced in a period ranging from a person's early twenties up to their mid-thirties, although it can begin as early as eighteen. It is defined by clinical psychologist Alex Fowke as "a period of insecurity, doubt and disappointment surrounding your career, relationships and financial situation".

While the quarter-life crisis is not an official clinical diagnosis and does not appear in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5-TR), it is increasingly recognized by mental health professionals and researchers as a genuine developmental challenge faced by young adults in contemporary society. The phenomenon has become a subject of academic research, with studies examining its prevalence through social media analysis and its relationship to modern factors such as student debt, competitive job markets, social comparison through social media, and the postponement of traditional adult milestones like marriage and home ownership.

While the concept of a young adult crisis has been attributed to psychologist Erik Erikson in his 1968 work Identity, Youth and Crisis, where he described identity challenges facing people in their twenties and early thirties as part of his "Intimacy vs. Isolation" stage, he did not use the specific phrase "quarter-life crisis" in his writings.

The term "quarter-life crisis" was popularized by the 2001 book Quarterlife Crisis: The Unique Challenges of Life in Your Twenties by Alexandra Robbins and Abby Wilner. The book brought widespread attention to the phenomenon and served as a guide for young adults experiencing difficulty transitioning to adulthood. Following its publication, the concept gained further traction through media coverage and has become particularly associated with millennial experiences, with outlets like Psychology Today and Forbes featuring articles on the topic.

The term was modeled after "midlife crisis," which was coined by psychoanalyst Elliott Jaques in 1965.

The main areas affected during a quarter-life crisis include career, relationships, and sense of identity. Individuals typically question whether their current career path or relationships are right for them, and struggle with making significant life changes. These major decisions ultimately impact one's sense of identity, leading to fundamental questions such as "who am I?"

During this period of questioning, individuals generally experience one of two types of crisis: "locked-out" or "locked-in." The locked-out experience involves being unable to access desired life commitments, such as finding meaningful employment, establishing romantic relationships, or making other major life transitions. In essence, external opportunities feel closed off. Conversely, the locked-in experience involves feeling trapped in unsatisfying circumstances, such as remaining in an unfulfilling job or relationship despite serious dissatisfaction.

These experiences produce both negative emotions and opportunities for growth. Common negative symptoms include anxiety, declining self-esteem (particularly when facing repeated rejections), and intense identity questioning. However, individuals who successfully navigate these challenges may experience post-crisis growth and enhanced life satisfaction in the longer term.