Redskins head coach Mike Shanahan made the decision on Wednesday, with the call made due to increasing worries within the team camp regarding Griffin's fitness.
Griffin's knee has been a cause for concern for Washington ever since he sustained an ACL injury last season.
Shanahan told reporters: "With Robert, I though that his hits were piling up on him. The best thing to do is to go into that third year injury free.
He won't understand our decision to bench him, but at the end of the day you've got to feel like your football team did the right thing.
"You can always go back. You can always question yourself. But the doctors said he was 100 percent ready to go in week one."
Griffin ends the campaign having completed 274 of his 456 passes for over 3,000 yards. He threw 16 touchdowns and 12 interceptions, being sacked 38 times.
He will be replaced by Kirk Cousins as the starter for the team's match with the Atlanta Falcons on Sunday, followed by two divisional clashes with the Dallas Cowboys and the New York Giants to end the season.