The country legend died of suspected respiratory failure at the Munroe Regional Medical Center in Ocala, Florida, publicist Don Murry Grubbs said in a statement.
"Tillis battled intestinal issues since early 2016 and never fully recovered," he said.
Tillis, a father of six whose stammer and self-deprecating charm endeared him to fans, recorded more than 60 albums, scored 35 top 10 singles, and saw 600 of his songs recorded by major artists during a career spanning six decades.
The former Air Force baker -- who had his heyday in the 1970s -- also dipped into film and television, appearing on shows such as "Hee Haw" and movies including "Smokey and the Bandit II" (1980) and "Every Which Way but Loose" (1978), alongside Clint Eastwood.
He was also active in business ventures that included radio stations and publishing companies, as well as his own theater in Branson, Missouri, where he performed thousands of shows, according to The Tennessean newspaper.
In 2012, then-President Barack Obama awarded Tillis the National Medal of Arts. He was also a member of the Grand Ole Opry -- a pantheon for country music stars -- and a Nashville Songwriters Hall of Fame inductee.
A representative for Tillis' daughter Pam, also a country singer-songwriter, wrote on her Facebook page that his death was "sudden and unexpected."
"The Voice" judge Blake Shelton described Tillis' death as "a truly devastating loss" on Twitter, while musician and actor Tim McGraw remembered him as "one of the coolest guys in country music ever."
"I'm saddened to hear of the passing of my friend, Mel Tillis," Grammy Award-winning country singer Crystal Gayle wrote on Twitter, adding, "There will never be another Mel Tillis!"
Meanwhile, the Grand Ole Opry took to Twitter to thank Tillis "for the songs, stories and years of incredible entertainment."
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)