Introduction: Suicide is a global health concern accounting for over 700,000 deaths each year worldwide. Suicide capability including heightened pain tolerance and fearlessness about deathmay explain the progression from suicidal ideation to a suicide attempt. Thus, investigating the neural circuitry associated with pain, fear, and suicide risk presents a unique opportunity to identify biomarkers of suicide capability and contribute to our understanding of the transition from suicidal ideation to suicide attempt. Methods: A total of 90 adults aged 18 to 65 will be recruited from Toronto, Canada. Participants will either be 1) patients with current suicidal ideation but no previous suicide attempt (ideators; n=30), 2) patients with current suicidal ideation and a suicide attempt within the past six months (attempters; n=30), or 3) healthy controls (n=30). Participants will complete selfreport measures and magnetic resonance imaging tasks measuring pain tolerance and fearlessness about death. Results: It is expected that those who have attempted suicide will exhibit significantly higher pain tolerance and fearlessness about death than suicide ideators or healthy controls. It is also predicted that self-reported suicide capability will be negatively associated with pain-and fear-related neural activation. Discussion: Findings of the present study may contribute to the validation of ideation-to-action models of suicide by providing neurobiological evidence supporting the distinction between suicide ideators and attempters. Conclusion: By examining the neural underpinnings of suicide capability, this work contributes to the understanding of biomarkers indicating those at greatest risk of suicide.