Arsenal's WSL record winning-streak was ended at the 15th game after a sensational late Manchester United comeback stunned the Emirates.
The visitors trailed 2-1 going into the closing stages before headers from defender Mille Turner and Alessia Russo, from a late corner, turned a pulsating encounter upside down. The England striker powered home Katie Zelem's delivery to steal the points.
The Gunners' perfect start to the season had looked in real danger for much of a high-quality contest in front of a 40,064 strong crowd. Only a heavily deflected Frida Maanum strike was able to get the league leaders level, after United had led at the break following Ella Toone's goal from close range.
But Arsenal looked to have saved the streak when Austrian full-back Laura Weinroither fired home a Katie McCabe cross from the left in the 73rd minute. But United refused to lie down, with Turner heading home Zelem's free-kick with just five minutes of normal time to play.
As the game ticked into injury time Russo flicked home the winner to give United a memorable win.
It means Arsenal can be unseated at the top of the table this weekend by London rivals Chelsea, who face Tottenham tomorrow. The Red Devils meanwhile join Arsenal on 18 points, only trailing the previously unbeaten Gunners on goal difference.
The Gunners were aiming for a 15th straight win in the WSL, having only conceded twice in that run, but struggled to find their rhythm in the opening 45 minutes. It was the visitors who had the first real sight of goal when the lively Leah Galton forced an excellent save from Manuela Zinsberger at full stretch inside the penalty area.
United didn't look phased in the early stages of their first visit to the Emirates, with Millie Turner heading just over from a corner. Nikita Parris also fired a deflected volley over the bar as the visitors took charge of possession and kept the crowd quiet.
Toone's simple strike finally gave them the lead they deserved after Zinsberger failed to claim Hayley Ladd's cross. This was the first time the hosts had truly been tested during their winning streak, having only conceded in two of the 14 consecutive WSL matches won, against Birmingham and West Ham.
But they made the perfect response straight after half-time, when Maanum picked the ball up in her own half before driving towards the United penalty area. Her shot took a huge deflection off the unfortunate Maya Le Tissier to leave Mary Earps helpless.
Marc Skinner's side did hit back when Katie Zelem fired just over the bar after good work from Alessia Russo. Arsenal threw on Viviane Miedema in search of a winner but failed to consistently test Earps despite being roared on by the home crowd. That was until McCabe's perfect cross was finished superbly by her fellow full-back Wienroither.
But the visitors refused to lie down easily and their sensational late comeback handed the Gunners a first defeat of the season. Turner's header looked to have secured them the point their play deserved, only for Russo's dramatic winner leading United players to celebrate widely in front of a jubilant away end.
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