Police said officers were called to Humberstone Road just after 6pm after reports of an altercation involving two men and a woman.
A man in his 20s was taken to hospital with serious injuries but was pronounced dead shortly after.
Police are appealing for any further information, including doorbell, CCTV, or dashcam footage from the area around the time of the incident.
Superintendent Rachael Glendenning, from Bedfordshire Police, said: “This is an isolated incident, and we would ask the public not to speculate at this time.”
She said officers will be at the scene for a significant period while the investigation continues.
