The girl was found with a gunshot wound in Chalgrove Road near Northumberland Park station in Tottenham, north London.
Police were called at 9.35pm but she could not be saved.
Less than half an hour after the alarm was raised in Tottenham, police received reports of gunfire around three miles away in Walthamstow, east London.
The 16-year-old victim was found with gun shot wounds while a 15-year-old suffered knife wounds in Markhouse Road.
What have police said about the shootings?
On the death of the 17-year-old girl, a Scotland Yard spokeswoman said: "Despite the best efforts of the London Ambulance Service, she was pronounced dead at the scene at 10.43pm.
"Her next of kin are aware and a crime scene is in place. No arrests have been made at this stage."
Dell Laptop Helpline