Foley suffered a strike last December and was hospitalized in May with pneumonia, according to his wife, Heather. He had been on hospice care at his home in the nation's capital ever since.
He served 30 years in the U.S. House, including more than five years as speaker.
"Today the House mourns the loss of our beloved former colleague," said House Speaker John Boehner in a statement. "With his passing, the House loses one of its most devoted servants and the country loses a great statesman."
The Democrat, who had never served a single day in the minority, was ousted by a smooth young Spokane lawyer, Republican George Nethercutt, who won by 4,000 votes in the mostly rural, heavily Republican eastern Washington district.
House Minority Leader Nancy Pelosi, D-Calif., called Foley "a quintessential champion of the common good" who "inspired a sense of purpose and civility that reflects the best of our democracy."
"Speaker Foley's unrivaled ability to build consensus and find common ground earned him genuine respect on both sides of the aisle," Pelosi said.
Foley also served as U.S. ambassador to Japan for four years in the Clinton administration.
The Associated Press contributed to this report.