Background: Suicide is the leading cause of death in prisons worldwide. Improved understanding of the factors associated with suicide is necessary to inform targeted suicide prevention and interventions. Here we aim to (a) document the prevalence of suicide attempts, suicidal ideation, self-harm, and mental disorder; and (b) identify demographic, mental health, and criminal justice correlates of suicidal ideation, in a sample of incarcerated adults in Australia. Methods: Data were obtained from the 2016 Detainee Health and Wellbeing Survey conducted in the Alexander Maconochie Centre, the Australian Capital Territory's only adult prison. Interviews with 98 incarcerated adults were conducted in October 2016. Descriptive statistics were calculated for all measures. Crude differences between participants who reported experiencing suicidal ideation in their lifetime and those who did not were compared using Fisher's exact test. Results: Nearly half of the participants (48%, n = 47) reported lifetime suicidal ideation and 31% (n = 30) reported attempting suicide at some point in their lives. Eighteen participants (18%) reported a lifetime history of having engaged in self-harm. Factors significantly associated with suicidal ideation included lifetime history of mental disorder, self-harm, experiencing a drug overdose, and being hospitalized in the past 12 months. Conclusion: The burden of suicidal ideation and prior suicide attempts among people in prison is substantial. Incarceration is a pivotal opportunity to identify people with a history of mental health problems and target interventions aimed at reducing adverse outcomes including suicide mortality.