Newcastle inflicted a sixth Premier League defeat of the season on Manchester United as Arsenal beat Wolves 2-1 on Saturday to extend their lead at the top to four points.
Anthony Gordon scored the only goal at St James' Park to lift Newcastle up to fifth in the table and within two points of the top four.
By contrast, United slip to seventh and are still to beat any side in the top nine of the Premier League this season.
Eddie Howe's men deserved to win by a bigger margin despite missing 11 first-team players due to injury or suspension and losing goalkeeper Nick Pope late on to a shoulder problem.
Kieran Trippier's free-kick came back off the underside of the bar and Alexander Isak's effort was deflected inches wide before the break.
Gordon finally made the breakthrough 10 minutes into the second period when he was picked out by Trippier to convert at the back post.
"I couldn't be happier with the players tonight," said Howe after his under-strength side took seven points from three games in a week against Chelsea, Paris Saint-Germain and United.