Presumably, everyone has, at some point in their lives, felt lonely. Loneliness is, in that particular sense, omnipresent. What it feels like to be lonely can, however, vary significantly. Loneliness is far from being a homogeneous phenomenon. Different kinds of loneliness need to be distinguished, considering its causes, contexts, a person’s capacities to cope with it, and many other factors. This paper introduces the notion of a specific kind of loneliness: experiential loneliness. Experiential loneliness, it will be argued, consists in (...) particular ways of experiencing the world, oneself, and others. Although feelings of being lonely in one way or another can emanate from one’s experience of the world being structured in a particular manner, such kinds of loneliness need not—at least, not always and the whole time—lead to emotional feelings that are concerned with one’s loneliness or the lack of meaningful social relationship. Loneliness can give rise to quite different emotional feelings that sometimes even cover up their provenience from underlying experiential loneliness. The notion of experiential loneliness, it is suggested, helps to tie back certain styles of thinking, desires, feelings, and behaviors to contexts of loneliness. Moreover, it will be argued that the notion can also elucidate the development of feelings of being lonely in contexts in which others are not only around but also available. To develop and enrich the notion of experiential loneliness as well as to exemplify its usefulness, a closer look will be taken at the case of borderline personality disorder, a condition in which sufferers are often plagued by loneliness. (shrink)