NFL outfit the Denver Broncos are set to be sold for a sports-franchise record $US4.65 billion ($A6.46b), according to multiple media reports.

The Walton-Penner family, led by Walmart heir Rob Walton, has made the winning bid.

The Walton-Penner family and the Pat Bowlen Trust have entered into a purchase and sale agreement, it was jointly announced on Tuesday.

The specific amount of the record-setting transaction was reported by various media outlets.

The price tag would be the highest price paid for any sports franchise, topping the $US3.2b ($A4.44b) paid for the NBA's Brooklyn Nets in 2019.

Walton, 77, has a net worth of $US65b ($A90.26b) and is the 19th-richest person in the world, according to Forbes.

The Walmart fortune is so vast that his siblings, Alice and Jim, also are among the world's 20 richest people on Forbes' list of billionaires.

If the Walton sale goes through, Rob Walton would become the second NFL owner from the extended Walton family - Ann Walton Kroenke, who is Walton's cousin, is married to Stan Kroenke, owner of the Los Angeles Rams.

"While this purchase and sale agreement is pending approval from the NFL's finance committee and league ownership, today marks a significant step on the path to an exciting new chapter in Broncos history." Broncos chief executive Joe Ellis said.