Police said Evie Baker, who is 16 years old, went missing from her home in Colwall just before midday today (May 23).
Evie is described as 5ft6 tall, slim build, blue eyes, long brown hair.
When she went missing, she was wearing a black hooded sweater and black jogging bottoms.
Her family are extremely concerned about her, and it is believed she may head towards local woodland or could possibly could have headed towards the train station.
Anyone with information is asked to please call 999.