Another man is fighting for his life while the youngest victim, stabbed in Brixton, south London, was just 13 years old.
Police were called to an address in Marsh Road in Pinner, a leafy suburb in north-west London, at about 6am on Sunday.
A man who had been stabbed was pronounced dead at the scene.
A large section of the road was cordoned off on Sunday morning while a forensics tent was erected outside Costa Coffee and an off-licence.
One resident described Pinner as "lovely" but said she was not shocked by the news as such incidents are "happening in all areas".
Mary MacNamara, who has lived in the area for four years, said: "We all see what's going on generally and it (such crime) seems to be happening in all areas.
"It's happening every day. Nobody does anything about it."
Local MP Nick Hurd said police were making house-to-house enquiries.
He tweeted: "Deeply saddened to hear of a fatal stabbing earlier this morning. Area cordoned off; police conducting house to house enquiries and reassurance patrols."
Deeply saddened to hear of a fatal stabbing in Marsh Road #Pinner earlier this morning . Area cordoned off ; police conducting house to house enquiries and reassurance patrols .— Nick Hurd (@NickHurdUK)March 24, 2019
A second man, aged in his 40s, is in a critical condition in hospital after he was found with stab wounds in Dalston Lane, at the junction with Lower Clapton Road, in north-east London at about 3.15am.
Meanwhile a 13-year-old boy was knifed in St Matthew’s Road, Brixton shortly before midnight.
Paramedics rushed him to hospital and his condition is not thought to be life threatening.
Two males, believed to be aged in their late teens or early 20s, were found stabbed in Harrow Road, Westminster, while another of around the same age was found with head injuries.
Emergency services were called at 10.30pm. Their injuries are also not thought to be life threatening, police said.
And shortly before 8.30pm, a man in his 20s was also taken to hospital with non-life threatening injuries after he was stabbed in High Street in Barkingside, north-east London.
Scotland Yard said no arrests have been made in connection with any of the incidents.