New Everton manager Sean Dyche enjoyed a dream start as a much-improved side stunned Premier League leaders Arsenal at a raucous Goodison Park.
Dyche was appointed as boss last Monday following the departure of Frank Lampard, who was sacked with Everton in the relegation zone.
But the hosts picked up their first victory in 11 games in all competitions courtesy of a link-up between two men who played for Dyche at Burnley.
Centre-half James Tarkowski rose at the far post to power home a header from Dwight McNeil's corner to spark the sort of joyous scenes that have been witnessed rarely at Goodison this term.
Everton had enjoyed much the better chances in the opening period too, but striker Dominic Calvert-Lewin could not convert from the excellent Amadou Onana's low cross and also flicked a header wide.
Arsenal were outfought for large periods and failed to find any rhythm, although January signing Leandro Trossard forcing Jordan Pickford into a sharp save late on.
The Gunners were unable to find the leveller and will see their lead at the top cut to two points if champions Manchester City beat Tottenham on Sunday.
Everton show much-needed fight and grit
Thousands marched down Goodison Road before kick-off, protesting against Everton's board and its running of the club.
But what a transformation there has been on the pitch in just five days under the experienced Dyche.
The former Burnley boss has already set about changing the mindset of a team who have been abject this season.
Writing in his matchday programme notes, Dyche asked for "hard work" and a demonstration of the "pride" of wearing the Everton shirt - and he got both.
Setting up in a 4-5-1 formation, Everton snapped into tackles and gave high-flying Arsenal no room to breathe - with Vitalii Mykolenko's late challenge on captain Martin Odegaard in the second minute setting the tone.
The home side's pressing and ferocious tackling was epitomised by Belgium international midfielder Onana, who made more tackles - four - than any other player on the pitch, with each challenge greeted by a roar from the home fans.
Calvert-Lewin could possibly have done better with his chances but could not find the target, while Abdoulaye Doucoure - restored to the team after a falling out with Lampard had led to him being omitted - sent a free header wide.
It did not cost them though, as Tarkowski nodded in at the back post on the hour mark before wheeling off to celebrate a goal that ended a run of four consecutive home defeats with a statement win.
It was just their fourth league victory in 21 games this season, taking them out of the relegation zone by a point, but they could return to the bottom three depending on other results this weekend.
Huge setback for Arsenal
Arsenal have swept aside almost everyone put in front of them this season, but this is a major setback for Mikel Arteta and his team.
The free-flowing football that has lifted them to the top of the table was absent and they did not look like scoring after falling behind, succumbing to their second league loss of the campaign.
They had defeated Manchester United and north London rivals Tottenham with impressive performances in their previous two league games, but may well have Pep Guardiola's City breathing down their neck by Sunday evening.
Arsenal's performances this season have fuelled talk of a first league title since 2004, but if they fail to beat Brentford in their next game, they could be second by the time they host City on 15 February.
Eddie Nketiah wasted a presentable opening in the opening period, blazing wide, while Bukayo Saka did the same in the second half.
Deadline day signing Jorginho came off the bench to make his debut, but the Italy international was unable to create any chances for his team-mates.
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