The company said Runnels died Thursday, but a spokesman declined to say where or how he passed away, saying the family had not authorized the release of that information.
Runnels, who also went by the nickname "The American Dream," was a member of the WWE Hall of Fame, and held the NWA championship three times. He became famous during the height of wrestling's popularity in the 1970s and 1980s, appearing in signature yellow polka dot tights with his sidekick "valet" Sapphire.
In a statement, WWE offered condolences to Runnels family, calling him "a caring husband and a creative visionary who helped shape the landscape of WWE long after his in-ring career had ended."
Runnels remained a fixture with WWE after retiring from the ring and was working at WWE's Performance Center in Orlando, Florida.
Throughout his several decades in the ring, the Austin, Texas, native endeared himself to fans as an everyman with a less than stellar physique, but a gregarious gift of gab behind a microphone.
Runnels was also the father of two other famous WWE wrestlers: Dustin Runnels, better known as Goldust, and Cody Runnels, who wrestles under the name Stardust.
Jim Ross, a longtime WWE broadcaster, worked alongside Runnels for several years after his in-ring career had ended. He spoke slowly Thursday afternoon in a phone interview as he described being "heartbroken" about losing what he said was "a broadcast partner, colleague and mentor."
"He was arguably the most charismatic performer of all time," Ross said. "His amazing unique verbal styling will never be duplicated or exceeded. He was exactly what he portrayed on TV: A blue-collar, common man, who rose from being son of farmer to being a part of American pop culture, whose memory will live forever. Therefore, for many he was truly the American dream."
Several other past and present WWE wrestlers and personalities took to social media to express their thoughts.
Ric Flair, one of Runnels' rivals in the ring, also called Runnels a mentor. "Much love to your family and more respect than can ever be measured. Love you Dream," read a post on Flair's official Twitter account.
That was echoed by Paul Levesque, who wrestled under the name Triple H and currently serves at an executive vice-president with WWE.
"Saddened to hear the passing of Dusty Rhodes," he tweeted. "Legend, teacher, mentor, friend...Love you Dream."
On his Twitter page, wrestling broadcaster Gene Okerlund called Runnels "One of the best ever."
Ross said today's generation of wrestlers owe a lot to Runnels.
"Hopefully today's performers will understand how committed he was to his craft, how much he was in love with wrestling business and how much he as a natural extension of himself," Ross said. "If they are paying attention that is what they'll do... No matter what you do —wrestlers or anybody else — you have to commit yourself to always be yourself. Dusty was always himself."