Police were called to a property in Stamford Hill at 10.52am on Friday to a report of a stabbing.
When officers attended the scene they found a man, believed to be in his 30s, with stab injuries.
He was treated at the scene by officers who carried out CPR before paramedics from London Ambulance Service and London’s Air Ambulance arrived. Despite their best efforts, he died shortly after.
Enquiries are ongoing to notify his next of kin.
A 31-year-old woman was arrested on suspicion of the murder and has been taken into custody.
The man and the woman are believed to be known to each other and officers are not looking for anyone else in connection with this incident at this time.
Homicide detectives from the Met’s Specialist Crime Command have been informed and a post-mortem examination will be carried out in due course.
A crime scene remains in the area.