Lay was at his family vacation home in Aspen, Colo., when he reportedly suffered a massive heart attack.
In a statement, a spokeswoman for Lay said more information would be released later.
"The Lays have a very large family with whom they need to communicate, and out of respect for the family we will release further details at a later time," Kelly Kimberly said.
In Colorado, a CNN affiliate said Lay had been admitted to the Aspen Valley Hospital in the early hours of Wednesday morning and had died there.
In May, a jury found Lay and former Enron CEO Jeffrey Skilling guilty of defrauding employees and investors by lying about the financial health of the energy and trading conglomerate they ran, even as it headed toward bankruptcy.
The former Fortune 500 company, which was once considered the country's seventh largest corporation, collapsed in 2001 after investigators found that much of its wealth was based on fraudulent partnerships rather than the profits Lay and Skilling reported.
Some 4,000 employees lost their jobs and a lifetime of savings in the scandal.
A separate jury also convicted Lay, who sold millions of dollars of stock in the company right before its collapse, of fraud related to his personal finances.
Lay and Skilling were scheduled for sentencing Oct. 23 and faced 25 to 40 years in prison.
Throughout the Enron trial, Lay and Skilling maintained their innocence and blamed negative publicity and the subsequent lack of investor confidence in the company for Enron's fall.
The Enron accounting scandal, and later scandals involving WorldCom, Tyco and other high profile, multi-million dollar corporations, led to the passage of the Sarbanes-Oxley Act, which strengthened control of how U.S. companies run their finances, CNN reported.
Lay was born in Tyrone, Mo., attended the University of Missouri and later went to work in the oil industry. He joined the Navy in 1961 during the Vietnam War and later was promoted from a supply officer to a position at the Pentagon, a 2002 Houston Chronicle article reported.
Lay later served as undersecretary for the Department of Interior before returning to the private sector, reported the AP.
He became chairman and CEO of Enron in 1985 when Houston Natural Gas merged with InterNorth of Omaha, Neb. to form Enron.
Lay is survived by his wife Linda and five children.