WorldStarHipHop founder Lee O'Denat -- known as "Q" -- has died ... TMZ has learned.
We're told Q, the CEO of WorldStar and its face, died in his sleep Monday night.
Q founded the premiere hip-hop website in 2005 when he started posting mixtapes, which gradually progressed into a mash-up of hip-hop videos, fight clips and other outrageous camera footage.
An autopsy is scheduled for later today ... although one source tells us Q died of a heart attack.
He was 43.