Leah Elstone, who is from the Longwood area of Huddersfield, was last seen near Colne Valley High School, around 8.30am on Tuesday.
Detective Inspector Mark Truelove, of Kirklees CID, said: “We are concerned for Leah’s welfare, as it is unusual for her not to be in contact with her family. I would urge Leah, or anyone who has seen or heard from her since Tuesday, or knows where she is currently to get in touch.”
Leah is described as 5ft 2, slim, with shoulder-length mousey hair.
Anyone who may have seen or heard from Leah since Tuesday or who knows where she is should contact Huddersfield CID via 101.