Goals from Ayoze Perez and Matt Ritchie ensured the Gunners have lost five in a row on their travels for the first time since December 1984.
The result ended the Magpies' run of 10 successive league losses to Arsene Wenger's side and moved them to 41 points in the table, taking it to the brink of survival.
Arsenal has now lost all five of its opening away league matches in a calendar year for the first time since 1925 – a damning 93-year low that underlines its problems this season.
It has lost 11 times in the top flight this season, which equals its worst tally under Wenger, set during the 2005-2006 campaign.
The north Londoners have conceded 45 goals in their 33 league games, which is one more than it managed in the whole of last season. Its worst record under Wenger was in 2011-2012, when they shipped 49.
The result sees Arsenal stay sixth and means they are the same number of points – 33 – above bottom-of-the-table West Brom as it is behind leader Manchester City.
With the gap to the top four still at 13 points, and with only five games left to play, the Gunners are now expected to concentrate their efforts on winning the Europa League. They face Atletico Madrid in the semi-finals.