This article presents evidence to support the British Medical Association (BMA), the Royal College of Psychiatrists, and the Royal College of Paediatrics and Child Health call for an end to the solitary confinement of children and young people held in UK detention facilities. A survey by Her Majesty's Inspectorate of Prisons found that 38% of detained boys had spent time in solitary confinement. These boys were both physically and socially isolated from others and had almost no purposeful interactions or environmental stimuli. Periods of confinement could last up to 80 days. The authors argue that the evidence demonstrating that isolation is damaging to children is unequivocal, with a risk of serious long-term developmental impairment and psychological harm. Solitary confinement is also known to be associated with increased risk of suicide and self-harm, it also creates problems with reintegration and fails to address the root causes of young people's disruptive or violent behaviour. The authors note that despite a growing international consensus from a range of groups including the UN Committee on the Rights of the Child and the European Committee for the Prevention of Torture that solitary confinement should never be used for children or young people, the practice is widespread throughout both the UK youth justice system and in many other systems worldwide. They argue that to end this damaging practice, non-solitary confinement options must be prioritised and properly resourced so that it is possible to end the solitary confinement of children and young people.