Martellus Bennett has gone from catching touchdowns to dropping motivational words ... the ex-Super Bowl champion has just authored a children's book -- and it's super inspiring.
The work is called "Dear Black Boy" ... and Bennett told TMZ Sports this week it's a tale aimed at encouraging young Black boys to follow their dreams in any field -- not simply the sports world.
"When I look at Black boys, I don't see athletes," the former New England Patriots tight end said.