Gwent Police says officers are concerned about the safety and wellbeing of missing 13-year-old Michael Driver because of his age.
He was last seen at his home in Rogiet, near Chepstow in Monmouthshire, on Saturday 12 October.
Anyone who has seen him or has any information about his whereabouts is urged to ring 101 or Crimestoppers on 0800 555 111.
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Wales have qualified for the Euro 2016 quarter finals after beating Northern Ireland 1-0 in Paris.
A rally has been held in Cardiff following the EU referendum to show support to migrant communities.
It's 0-0 at half time in Paris as Wales face Northern Ireland in the last 16 of Euro 2016.