Johnny Hardwick, known for playing Dale Gribble on "King of the Hill," has died.

Law enforcement sources tell TMZ they were called to Hardwick's Texas home Tuesday for a welfare check and discovered his body. We're told Hardwick was pronounced dead at the scene ... and no foul play is suspected. We don't yet know the cause of death.

Johnny started performing stand-up comedy in 1990 in Texas, eventually landing his first stand-up appearance on "The Jon Stewart Show" a few years later.

Most remember Johnny from his work on the long-running animated sitcom, "King of the Hill" ... playing Dale, the conspiracy theory-obsessed friend of the show's lead, Hank Hill.

Dale took on just about every job imaginable -- tackling gigs like exterminator, camp counselor, bounty hunter, and, of course, propane salesman.

Johnny lent his voice to a whopping 258 episodes of the series. FYI, "King of the Hill" aired 259 episodes in total.

Johnny was with the show from the beginning, portraying Dale on the first episode that aired in January 1997 ... and stuck with the series until its final episode in 2010. He was also listed as returning for a revival of the show, although it's unclear if he ever recorded for it.

Apart from the show, Johnny would cover songs on his YouTube channel ... donning his character's signature orange hat and shades, performing just like Dale would on the show -- and making references to the character's "pocket sand" attack move.

Johnny was 64.

RIP