All under-18s have now been removed from Scotland's young offenders institutions and transferred to more child-friendly settings.
The change follows suicides of young people while detained and the passage of a new law that bans children being sent to prison.
As recently as July, there were still nine 16 and 17-year olds still held in custody at Polmont Young Offenders Institution (YOI) near Falkirk, but the final child was moved to a secure children's care unit on Friday.
The Scottish Prison Service said it was a "landmark day with children no longer admitted into our care".