Hardwick’s death was confirmed by the medical examiner’s office in Austin, Texas, according to USA Today.
He died at his home, and while no cause of death was provided, foul play is not suspected, according to Deadline.
For 13 seasons on the comedy created by Mike Judge and Greg Daniels, Hardwick played Dale Gribble, a chain-smoking, paranoid exterminator who lives next door to the titular Hill family in fictional Arlen, Texas.
He was part of the team that won an Emmy in 1999 for outstanding animated program.
Though “King of the Hill” ended its run in 2010, Hardwick’s performance as Dale Gribble has lived on through internet memes, including his comical use of “pocket sand” to escape confrontation.
He also was set to be part of the “King of the Hill” revival at Hulu, which was announced earlier this year.
Judge paid tribute to Hardwick on Instagram, where he posted an image of Dale spending time with his neighbors in their regular spot in the alley.