Police found the injured 18-year-old after they were called to Hertford Road, Enfield, on Saturday at 22:30 BST over reports of a fight.
He was taken to hospital but was pronounced dead an hour later. Two others also suffered stab wounds.
In a separate incident, a man was shot and stabbed to death in broad daylight near Bow Road Tube station.
The victim, 41, was killed in Eagling Close on Saturday afternoon in what police described as a "violent murder".
Two men have been arrested and are in custody at east London police stations.
The two teenagers who were stabbed in Enfield were found in Palmers Lane.
The 17 and 19-year-olds were taken to hospital but their injuries are not being treated as life-threatening.
Scotland Yard said no arrests have been made and have appealed for witnesses.
In another incident earlier, a man was taken to hospital in a life-threatening condition after being stabbed in the head and neck in Enfield.
Police said they believe the victim, who is thought to be aged in his 30s, was attacked following an "altercation" with a group of men in Exeter Road.
No arrests have been made.
A man has been stabbed to death and two others injured during a large brawl in north London.