The 18-year-old was taken to hospital after a firearm was discharged in Wolverhampton, at around 4pm yesterday.
The victim remains in a critical but stable condition, officers confirmed.
Cops found the weapon – believed to be a double-barrel shotgun – in a nearby street and launched an investigation, Birmingham Live reports.
The probe is ongoing and no arrests have been made so far, West Midlands Police said.
A police spokesman said: “We’re investigating after a woman was found with gunshot injuries in Hughes Avenue, Wolverhampton, just after 4.15pm yesterday (April 3).
“The 18-year-old was taken to hospital with chest injuries and remains in a critical but stable condition in hospital.
“A gun was recovered nearby and we’re carrying out further enquiries to establish whether it’s connected.
“A scene remains in place while we continue to establish the full circumstances. Anyone with information can contact us via Live Chat, or by calling 101, and quoting log 2814 of 3 April.”
It is the third time a gun incident happens in the area after shots were fired in Wolverhampton and in Bearwood.
Armed cops cordoned off Hall Park Street in Ettingshall after gunshots broke the quiet of a residential street on March 29.
Officers arrived just after 9am following reports of a man brandishing a firearm.
Firearm units again sprang into action after two men were taken to hospital after a shooting in Poplar Road, Bearwood, on March 31.