Marty Schottenheimer -- one of the NFL's all-time greatest head coaches -- died on Monday after a lengthy battle with Alzheimer's ... his family announced Tuesday.
He was 77 years old.
The coach had fought Alzheimer's since 2014 ... but was moved to a North Carolina hospice facility last month after his family said he was suffering from "complications from his disease."
Schottenheimer's wife, Pat, said at the time, "As a family we are surrounding him with love and are soaking up the prayers and support from all those he impacted through his incredible life.