Newcastle showed they have the appetite for a scrap in the bottom half of the table as Isaac Hayden's dramatic injury-time header earned a vital win against a dominant Chelsea.
Frank Lampard's side were on top for most of the game but had little to show for it as Tammy Abraham skewed wide from an acute angle and N'Golo Kante's shot was well saved by Martin Dubravka.
Prior to the winner, it was the hosts who came closest to scoring as Joelinton headed against the bar after Federico Fernandez's cross after 22 minutes.
But Steve Bruce's side showed their steel by keeping Chelsea at arm's length with a resolute defensive display.
And when Hayden headed in Allan Saint-Maximin's cross past Kepa Arrizabalaga, it sent St James' Park into raptures as they moved seven points clear of the relegation zone.
Their only worry was an injury to Jetro Willems, who was carried off in the first half.
Bruce said after the game that the problem looked "horrendous" with him fearing a cruciate knee ligament injury.
For Chelsea, it was another frustrating day during a mixed season under Lampard, who took over in the summer.
It was a first defeat since Boxing Day but they will rue another missed chance to improve their top-four claims after also drawing at Brighton earlier this month.
The Blues remain five points ahead of fifth-placed Manchester United, who face Liverpool on Sunday.
But the lack of firepower up front may sharpen Lampard's intentions to recruit a striker during the transfer window after being linked with the likes of RB Leipzig's Timo Werner.