BACKGROUND Approximately 10% of severely obese bariatric-surgery-seeking individuals report a lifetime history of suicide attempts, a higher rate than in the general community. Being overweight is associated with weight-related stigma, making an individual more vulnerable to social isolation, a potential risk factor for suicidal ideation and/or behavior. AIMS In this cross-sectional study of surgery-seeking adults with severe obesity, we examined whether weight-related stigma increases (1) the likelihood of suicidal ideation and/or behavior or (2) the degree of loneliness; and whether hypotheses (1) and (2) are supported (3) if loneliness mediates the effect of weight-related stigma on suicidal ideation and/or behavior. METHODS Online questionnaires were administered to 301 women and 95 men seeking bariatric surgery. RESULTS Approximately 30.3% reported having at least a passing thought of suicide, and 5.55% a suicide attempt during their lifetime. The suicide attempt rate appears lower than other bariatric surgery samples, but possibly higher than community and other surgery sample rates. For severely obese surgery-seeking women, weight-related stigma was associated with suicidal ideation and/or behavior, though this was not mediated by loneliness. CONCLUSIONS Future studies are needed to model and compare suicidal ideation and/or behavior in bariatric-surgery-seeking individuals and control groups.