George Stephanopoulos -- Wait, That Guy's NOT Morgan Freeman?

George Stephanopoulos is clearly not a basketball fan ... 'cause if he was, he might've known the old white-bearded African American man hangin' out at the Presidential Inauguration was NBA icon Bill Russell ... and not Morgan Freeman.

George was providing the play-by-play for ABC this morning ... when he started pointing out some of the famous people in the D.C. crowd ... and mixed up one legendary black guy for another.

George was quickly corrected by someone on the production -- and he apologized for the gaffe.

Happy Martin Luther King Jr. day everyone.