Loneliness is a common and distressing experience which has an existential dimension. Existential loneliness is understudied and a brief, valid measure which is grounded in experiences of the phenomenon and captures its distressing nature is needed. This study therefore developed the Brief Scale of Existential Loneliness. Scale items were developed based on a literature review and qualitative inquiry. Potential items were reviewed by academic experts, experts by experience, and potential participants for relevance and clarity. Scale structure was assessed through exploratory and confirmatory factor analysis with 714 participants (17–84 years old, M = 42.25, SD = 20.22) and reliability and validity were investigated. Tests of dimensionality revealed a 6-item unidimensional scale. The scale possesses high internal consistency and construct validity. Consistent with predictions, scale scores are negatively correlated with meaning in life and positively correlated with loneliness (broadly defined), poor mental health, emptiness, and related constructs. The Brief Scale of Existential Loneliness is a short, valid, and reliable measure of existential loneliness which may be usefully employed alongside measures of other loneliness dimensions.