Jesse Farrelly -- son of "Something About Mary" director Bobby Farrelly -- died this week of an apparent drug overdose in Orange County, CA ... TMZ has learned.
According to law enforcement ... emergency personnel responded to an apartment in Costa Mesa, CA late Wednesday night after getting a call about an "unresponsive young male ... possible overdose."
We're told 20-year-old Jesse was transported to a nearby hospital ... where he was pronounced dead a short time later. The coroner has completed the autopsy and has ruled out foul play.
Jesse's father and uncle make up the Farrelly Brothers comedy team ... and he had appeared in a couple of their movies ... including "Something About Mary" and "Hall Pass."
The Farrelly family has released a statement saying, "It is with profound sorrow that we accept the passing of our beloved Jesse following his struggle with addiction. We fully trust that he is now in the hands of our Lord."
The statement continues, "We are immeasurably grateful for the abundance of happiness and laughter he brought into our lives, and we will rejoice eternally for all the moments we got to breathe in his wondrous spirit. The family thanks you for your well wishes and kindly asks that you respect our privacy during this difficult time."