Marissa Gallagher was last seen leaving school in the Kirkoswald Drive area of Clydebank around 10.45am on Tuesday (May 25) and has not been seen or heard from since.
She is described as being 5ft tall, of slim build with brown hair. She was last seen wearing a black Canada Goose jacket, a red Nike hoody with a small white tick, black leggings, white Nike Air Force 1s and was carrying a black back pack.
Inspector Morven Sutherland, of Dumbarton Police Station, said: “Along with her family, we are becoming increasingly concerned for Marissa’s welfare.
“I would urge anyone who may have information about her whereabouts or who may have seen her to contact us immediately. Similarly, if Marissa is reading this, let us know you are safe and well.”
Anyone with information is asked to contact Police Scotland on 101 quoting reference number 1237 of 25 May