The body was found after police searched a sports ground in Thornfield Avenue, Mill Hill, at about 17:00 BST on Sunday.
The death is being treated as murder, a spokesman for the Metropolitan Police said.
A post-mortem examination will be arranged in due course, the spokesman added. The woman has not been identified.
She has been described as a young adult.
Detectives from the Homicide and Serious Crime Command are investigating.
A cordon remains in place in the area where the body was found.