Chicago Bears legend Gale Sayers has died after a lengthy battle with dementia ... the Pro Football Hall of Fame announced Wednesday.
He was 77 years old.
Sayers -- despite only playing in 68 career games due to various injuries -- is considered one of the greatest running backs of all-time.
He made the All-Pro team FIVE times and was selected to the Hall of Fame on the first ballot in 1977 ... and is still the youngest person to ever be inducted.
HOF President and CEO David Baker said Wednesday the death rocked the football world .