Abigail Hindle, from the North Yorkshire village of Cross Hills, was last seen at Skipton bus station on Sunday morning.
Police began an investigation to find her and are now becoming increasingly concerned for her welfare.
A spokesperson for North Yorkshire Police said: "Her family have described her disappearance as ‘out of character’.
"Known as Abbie, she has long, wavy brown hair and blue eyes. She was last seen wearing a brown hooded jacket, black top and leggings and beige trainers. She was carrying a silver purse.
"Anyone who thinks they may have seen her or has information about her whereabouts should contact North Yorkshire Police on 101 and select option 1.
"Please quote reference 12180174149."