Pro bodybuilder Rich Piana was placed into a medically induced coma this week after suffering a medical emergency at his Florida home, law enforcement sources tell TMZ Sports.

46-year-old Piana has competed and won several bodybuilding competitions over the years -- including Mr. California -- and has become an Instagram sensation, racking up more than 1 million followers.

Law enforcement sources tell us ... emergency personnel responded to a possible overdose call at Piana's home on Monday afternoon. When they arrived, Piana was unresponsive and was transported to a nearby hospital where he was placed into a medically induced coma.