What kind of experience do we refer to when we talk about self-esteem? How are our interpersonal relationships shaped by this experience? And what is the role played by high and low self-esteem in mental illness? While significant efforts have been made in the field of psychology to clarify some of these issues, the notion of self-esteem has been under-researched from a philosophical perspective.Surprisingly, this is the case also in current philosophy of emotion, philosophy of mind, and philosophy of psychiatry, where a number of concepts and dynamics relevant to the understanding of this form of experience have been investigated. With the aim of rectifying this situation, in this project I will endeavor to provide a philosophical account of self-esteem. More specifically, drawing on the insights and theoretical frameworks developed in classic and contemporary phenomenology, I will investigate three main thematic areas. (1) I will start by clarifying which types of mental states are constitutive of self-esteem, exploring in particular the idea that this predicament is best understood as a background affective orientation or "existential feeling". (2) I will then move to examine the connection between self-esteem and intersubjectivity, focusing on the various ways in which self-esteem influences and is influenced by interpersonal relationships such as friendship and love, and by particular forms of cultural and professional experience. (3) Finally, I will identify various dynamics through which alterations of self-esteem give rise to disruptions of affectivity and self-understanding in psychiatric illnesses such as depression,anxiety, and narcissistic personality disorder, complementing and expanding existing phenomenological analyses of disturbances of emotions and the self.