The Pro Football Hall of Fame announced his death Friday but did not disclose details.
A member of the Hall of Fame, Gregg starred at tackle and guard. He played on six NFL/NFC championship teams and three Super Bowl winners. He was elected to the NFL’s all-decade team of the 1960s and its 75th anniversary team.
He went on to coach in the NFL for 11 years. Gregg coached Cleveland (1975-77), Cincinnati (1980-83) and Green Bay (1984-87). He guided the Bengals to their first Super Bowl during the 1981 season.
Gregg began his NFL career in 1956 and played a final season with the Dallas Cowboys in 1971.
He entered the Hall of Fame in 1977. Its president, David Baker, described him as a “giant” who “exemplified greatness during a legendary career.”
“He was the type of player who led by example and, in doing so, raised the level of play of all those around him,” Baker said in a statement. “Forrest symbolized many great traits and virtues that can be learned from this game to inspire people from all walks of life.”
The flag at the Hall will be flown at half-staff.
Survivors include his wife, Barb.