<p>Mental health among adolescents is of growing importance, with loneliness being a critical indicator for assessment. This study explores the heterogeneity of loneliness among Chinese adolescents and investigates the predictors and outcomes associated with various types of loneliness through latent profile analysis. We administered the UCLA Loneliness Scale, Chinese Big Five Personality Inventory, Shyness Scale, Trust Scale, Delaware Bullying Victimization Scale, and Feelings of Inadequacy Scale to assess two samples of junior high school students (Sample 1 consisted of 500 students, 45% of whom were boys, M = 13.97 ± 1.00 years old; Sample 2 consisted of 528 students, 43.2% of whom were boys, M = 14.24 ± 1.02 years old). Utilizing this data, we analyzed adolescent loneliness and related characteristics employing latent profile analysis (LPA) and a multivariate logistic regression model. The results were as follows: (1) three latent profiles of adolescent loneliness were identified across both samples: low loneliness, moderate loneliness and social loneliness. (2) The three predictor variables—Big Five personality traits, shyness, and trust—were significantly correlated with the varying profiles of adolescent loneliness. (3) Regarding the outcome variables, adolescents experiencing low loneliness were the least impacted by feelings of inadequacy and bullying victimization, with those experiencing moderate and social loneliness being subsequently more affected. The results suggest that adolescents identified as social loneliness type should be targeted with interventions aimed at adjusting their personality traits. Conversely, adolescents with moderate loneliness should be more attentive to interpersonal factors such as shyness and trust, given their increased vulnerability to bullying and higher likelihood of experiencing feelings of inadequacy.</p>