Lee senior had been receiving treatment at Seoul National University Hospital, according to his close aides.
First elected to the National Assembly in 1988, the six-term lawmaker served as its vice speaker from 2006 to 2008.
Once a prominent political figure during his younger brother's presidency, the disgraced lawmaker was sentenced to prison in 2012 for his involvement in a corruption scandal.
His memorial altar has been set up at Seoul's Asan Medical Center.
