Patricia Martin, age 17, has been missing from Pleasanton since Monday, according to the National Center for Missing and Expolited Children website.
Martin is listed on the site as an "endangered runaway" and is also listed on the "Seeking the Lost" Facebook page.
Pleasanton Police are investigating the case.
"A detective has been assigned to this case and is working on developing leads," said Lieutenant Jeff Bretzing.
Parvin Ahmadi, Superintendent of the Pleasanton Unified School District wrote: "We wish and pray for her to be reunited with her family and friends."
Martin is 5'1" and 160 pounds with blue eyes and light brown hair. Her nose and lips are pierced and her hair may be dyed black. She may go by "Tricia."
If you have information to locate her please call 1 800 THE LOST or at 1-925-931-5100.