Emergency crews were called to reports that two men had been stabbed in Hainault at around 10.20pm on Friday.
A 23-year-old man was pronounced dead at the scene, Met Police said, and a murder investigation is now under way.
Another man, aged 22, was taken to an east London hospital where he is in a critical condition.
A police spokesman said: “Work continues to inform all next of kin. A postmortem examination will be scheduled in due course.”
No arrests have been made as yet and a crime scene remains in place, the spokesman added.
Officers from the force’s homicide and major crime command are investigating.
Meanwhile, another man is in hospital after suffering gunshot injuries in a separate incident in Amhurst Road, Hackney, at about 9.30pm on Friday.
It is believed he was shot at by two people on a moped, police said.
His condition is not believed to be life-threatening.
The attacks come amid heightened concern about violent crime in London, with the number of murder investigations in the capital so far in 2018 reaching 100 in September.