This bulletin presents information on the youth detention population in Australia from June 2015 to June 2019. Among the 949 young people in detention on an average night in the June quarter 2019, most were male (90%), aged 10–17 (83%), unsentenced (63%), and Aboriginal or Torres Strait Islander (53%). Over the 4-year period, the number of young people in detention fluctuated across quarters with no clear trend.