A statement from the Marin County sheriff’s department said the 63-year-old funnyman was found shortly before midday at his home in Tiburon, northern California.
“At this time, the sheriff’s office coroner division suspects the death to be a suicide due to asphyxia,” the statement said.
According to US media reports, the veteran actor had been battling depression.
One of the most beloved American entertainers of his generation, Williams rose to fame in the iconic US television sitcom “Mork & Mindy”.
He later reeled off a string of big-screen hits, which included 1987’s “Good Morning Vietnam”, where he played a motormouth US military disc jockey, 1989’s “Dead Poets Society” as a maverick English teacher and 1997’s “Good Will Hunting” which earned him a best supporting actor Oscar.