Police are appealing for missing 16-year-old Dhuy Duong Nguyen to get in touch.
Lida, as she is known by her peers, was last seen on Tuesday, March 28, in Cosgrove.
She was wearing a brown coat with a fur hood, blue jeans with cuts in the knees and black trainers with white soles.
She normally wears a solid silver bracelet and necklace.
Officers are growing increasing concerned for her welfare and are urging Lida, or anyone who knows of her whereabouts, to contact Northamptonshire Police on 101.