The Hierarchical Taxonomy of Psychopathology (HiTOP) framework offers the potential to better understand how neurobiological mechanisms relate to psychopathology. The P300 is an event-related potential component that indexes attention, stimulus evaluation, and categorization. A blunted P300 has been associated with psychiatric disorders across externalizing, internalizing, and thought disorder domains. However, there has been little research investigating whether the P300 is related to higher-order dimensions of psychopathology. In a sample of 225 adults aged 18-35 years (Mage = 23.09, SD = 3.83, 82.2% female) who were oversampled for psychopathology, the present study examined the associations between the P300 and both psychopathology spectra and a general factor. Participants completed multiple experimental tasks, while electroencephalography was recorded to measure the P300 elicited by auditory, tactile, and visual stimuli. Participants also completed the self-report Comprehensive Assessment of Traits Relevant to Personality Disorder to assess pathological personality dimensions. We used structural equation modeling to examine the relationship between a latent P300 factor and both psychopathology spectra (negative emotionality, detachment, psychoticism, disinhibition, and antagonism) and a general factor. The results indicated that the P300 was inversely related to the general factor. Further analyses revealed no relationships between the P300 and any individual spectrum when accounting for the general factor. Overall, the present study indicates that the P300 is associated with the general factor of psychopathology, which might explain its association with multiple categorical disorders. The study also demonstrates the potential importance of neuroscience-informed dimensional systems to understand clinical phenomena. (PsycInfo Database Record (c) 2024 APA, all rights reserved).