Police say the man, believed to be aged 46 and living on his own, was found lying outside his address in Gloucester Street, Linwood, at 6.50am, with a knife nearby.
Two witnesses returning home having finished their night-shift saw the man, went to his aid and called ambulance and police.
Police say the man is believed to have a single chest wound and his injury is described as critical.
They say an investigation has started to establish how the injury was caused and whether anyone else is involved.
Police have a team of seven investigators working on the case.
They say the victim will not be named until his next of kin are informed and no further comment will be made until the scene examination is completed.