Officers from the Met Police were called at 3.50pm to Northwick Park, Harrow, on Thursday following reports of a stabbing.
Officers attended and found a male, believed to be aged 17, suffering stab injuries.
He was given first aid at the scene by officers prior to the arrival of LAS , but despite best efforts of emergency services, he was pronounced dead at the scene.
Police said the teenager’s next of kin have been informed.
There have been no arrests made at this time and a crime scene remains in place.