The man, in his 20s, was knifed in the Sheridan Street area of the New Lodge just after 2.30 pm.
The victim was rushed by ambulance to the Royal Victoria Hospital’s accident and emergency department.
An ambulance service spokesman said: “The Northern Ireland Ambulance Service received a 999 call at 2.36 om on Monday, January 28, 2019,following reports of an incident at Sheridan Street, Belfast.
“NIAS dispatched two Rapid Response Paramedics, and one Emergency crew to the scene.
“Following assessment and initial treatment at the scene, one patient was transferred to the Royal Victoria Hospital, Belfast.”