Rates of youth suicide are alarming. A key predictor is suicidal ideation (i.e., thoughts about, or plans of, ending one’s life) with rates up to 20% every year. Suicide and suicidal ideation disproportionately affect rangatahi Māori. It is imperative to overcome barriers young people encounter in accessing meaningful support. Given youth are digital natives with high levels of smartphone ownership, mental health applications (apps) are promising. Several promising apps for suicidal ideation have been developed and pilot tested. Before developing further apps, it is imperative to test how well these work across our region. In a trans-Tasman four-armed superiority randomised controlled trial, three apps (Tune In, Village, LifeBuoy) will be compared with a control app. The primary outcome is suicidal ideation, with secondary outcomes self-harm, wellbeing, acceptability, and responsiveness to Māori. This will result in effective apps being available, reduce inequities and drive further development in a rational way.