Askew was hospitalized Saturday with pneumonia, then suffered a stroke, The Florida Current reported.
Askew, who served as governor from 1970 to 1979, was known for implementing Florida's corporate income tax and his "Sunshine Amendment," which mandated financial disclosure by public officials.
He was part of a wave of moderate "New South" Democrat governors along with former President Jimmy Carter in Georgia, Dale Bumpers in Arkansas and John West in South Carolina. The governors were focused on progressive education, economic development and environmental concerns.
After leaving office, Askew briefly ran for president in 1984, but dropped out after a low finish in the New Hampshire primary. He then started a congressional campaign in 1988, but again dropped out.
He began teaching public policy and administration at Florida universities after his political career.
Askew is survived by his wife Donna, children Kevin Askew and Angela White and several grandchildren.