Bipolar disorder carries an ultra-high risk for the experience of suicidal thoughts and behaviours. Up to 80% of people who experience bipolar disorder will experience suicidal ideation during their lifetime and 50% will attempt to end their life on at least one occasion. Psychological theoretical models of suicide hypothesise that perceptions of social support play a significant role in the pathways underlying suicidal ideation and behaviour. However, there is a paucity of theoretically-motivated, scientific studies which investigate the relationship between perceived social support and suicidality in bipolar disorder. Empirical research examining the nature of this complex relationship, as well elucidating as the psychological mechanisms which underlie the relationship, are important for three reasons, (1) to refine theoretical models of suicide and ascertain whether they are applicable to individuals with bipolar disorder, (2) to identify potential psychosocial markers for suicide risk in bipolar disorder, and (3) to explore potential target areas for suicide-preventative psychological interventions. A series of five studies were designed to investigate the following key areas, (1) the ways in which social support-related constructs lead to, worsen and protect against the development of suicidal ideation and suicide attempts in bipolar disorder, (2) whether perceptions of defeat and entrapment, two theoretically-motivated constructs, underlie the development of prospective suicidal ideation in bipolar disorder, (3) the relationship between negative appraisals of social support, defeat, entrapment and suicidal ideation in bipolar disorder; iv.) the role of positive and negative appraisals of bipolar-relevant experiences in the pathways underlying perceived social support and suicidal ideation. These studies were informed by the first systematic literature review of the role of psychological and social factors in the suicidal thoughts and acts of people who experience bipolar disorder. A sixth study explored experiences of suicide research participation from the perspective of individuals with bipolar disorder. Qualitative findings highlighted that negative social experiences and a perceived lack of understanding from key members of social networks triggered suicidal thoughts. Perceived burdensomeness and the reinforcement of negative self-appraisals by others increased the severity suicidal thoughts and facilitated suicidal behaviour. However, considering the potential impact of participantsâ own suicide upon others was an important protective factor against suicidal behaviour. Similarly, reflecting on past positive social experiences fostered feelings of hope for the future and protected against the worsening of suicidal thoughts. Longitudinal quantitative studies supported the hypothesis that defeat and entrapment underlie prospective suicidal ideation in bipolar disorder. A longitudinal study also highlighted the existence of an indirect pathway, whereby negative perceptions of social support led to heightened defeat, entrapment and suicidal ideation. Moderated mediation was used to demonstrate that extreme and personal appraisals of depression moderated the relationship between defeat and suicidal ideation in bipolar disorder. Findings supported a socio-cognitive model of suicidal ideation and behaviour, the Schematic Appraisals Model of Suicide (SAMS; Johnson et al., 2008). Clinical and theoretical implications are discussed throughout.