Paula Wambura was last seen on Friday evening in Leeds. She has not been in contact since.
West Yorkshire Police say the teenager could be anywhere in West Yorkshire, but is known to have contacts in Sheffield.
A force spokesman said: “We are are concerned for Paula’s safety and appeal to anyone who has seen or heard from her since Friday, or who knows where she is now to get in contact.
“We would also appeal directly to Paula to get in contact and let us know that she is OK. Enquiries are ongoing.”