Obsessive–compulsive personality disorder (OCPD), rooted in Janet’s psychasthenia, Freud’s “anal character,” and Schneider’s notion of anankastia, is among the most common yet least frequently diagnosed personality disorders. Contemporary classifications emphasize its dimensional nature. The central features are perfectionism, rigidity, and excessive need for control. Prevalence in the general population is estimated at 6.5%. In clinical populations, rates are higher: 16% among outpatients and up to 30% in inpatients. OCPD most often co-occurs with obsessive–compulsive disorder (OCD) (17‒45%), depression (31‒76%), bipolar disorder (32.4%), anxiety disorders (17‒30%), substance use (25–29%), eating disorders (20‒61%), and autism spectrum disorder (19‒43%). Comorbidity with OCD is associated with earlier onset, delayed diagnosis, and poorer insight. It is also linked to greater chronicity, elevated suicide risk, and bipolarity. Etiology is multifactorial, including genetic (27‒78%), neurobiological, and environmental factors. Reduced quality of life is emphasized, linking the severity of OCPD traits with psychosocial burden. Diagnosis should include psychological testing and collateral information, supported by clinical observation. Psychoeducation and psychotherapy constitute a central component of treatment. The strongest evidence supports cognitive–behavioral therapy targeting perfectionism and rigidity. Psychodynamic methods, schema therapy, and third-wave approaches may also be useful, while pharmacotherapy has a limited role.