This report presents information on the youth detention population in Australia from June 2017 to June 2021. Among the 819 young people in detention on an average night in the June quarter 2021, most were male (91%), aged 10–17 (83%) and unsentenced (72%). Half (50%) were Aboriginal and Torres Strait Islander. Over the 4-year period, the numbers fluctuated across quarters, decreasing overall, from 958 in the June quarter 2017.