Riverside police responded to a report of male subject down on the 4500 block of Jurupa Avenue at 5:42 p.m.
Responding officers located a wounded man next to a folding knife.
A witness said the victim had been involved in a physical altercation with the occupants of a dark blue or black Honda.
The suspects were described as Hispanic males.
The victim was hospitalized with multiple stab wounds to his chest and is listed in critical condition.
No motive is known at this time. An investigation was ongoing.
Anyone with information was asked to contact Detective Dave Smith at (951) 353-7103 or Detective Greg Rowe at (951) 353-7136.