VIVIANNE MIEDEMA was Auba the moon as she ended Manchester Citys unbeaten run.
Arsenals Dutch striker bagged the winner to send her side up to second in the WSL a point behind Chelsea.
And the 43rd-minute goal draws her level with Pierre-Emerick Aubameyang on 49 goals in total for the Gunners.
Steph Houghton and Gemma Bonner created an opening for Kim Little, who delivered a neat through ball for Miedema to finish.
There were doubts whether the 23-year-old last seasons top scorer and nominated for the Ballon dOr would even start after picking up a calf strain against Charlton last Sunday.
Defeat was a massive blow for City, who until this clash had not conceded in the league, and a win would have seen them clear at the top.
Miedema said: Ive been struggling this week.
I havent really trained so I had a bit of extra energy and I was happy I could do this for the team.
I think it was smart for me to not train this week and I love that our manager Joe Montemurro still played me and I think I paid him back.
It was a cagey start at Meadow Park with a distinct lack of goalscoring opportunities and little separating the two sides.
Miedema had the first real chance but the striker, who rarely misses in front of goal, uncharacteristically smashed a shot over the bar.
Tess Wullaert responded for the visitors and flashed an effort just over the woodwork from the right.
But the Gunners held the edge after the break, despite Ellen White making her long-awaited debut in the 66th minute following a lengthy stint on the sidelines after knee surgery.
The England striker, who signed from Birmingham and scored six goals in the World Cup, made little difference.
And City did not have a single shot on target after the break.
They looked a shadow of the side who have dominated the league so far and were clearly missing star midfielder Keira Walsh, who was suspended following her straight red against United.
Jordan Nobbs came close to doubling the Gunners lead in stoppage time but her effort flashed agonisingly wide of the far-left post.
Montemurro said: I think we had a lot of the ball and we just had to bide our time.
The biggest thing was off the ball, our collective work, our collective pressing, not allowing them to play, it was special.
City boss Nick Cushing said: We need Ellen back fully fit. Thats two games now where weve rotated the forward line and we havent really had a shot at the goal.
We didnt have a shot against Man United and we didnt have a shot against Arsenal here.
Having Ellen back will hopefully give us more firepower but weve got to get on the training pitch as a group and improve.
EMMA OK AFTER KICK UP BACKSIDE
West Ham 1 Chelsea 3 by Sandra Brobbey
EMMA HAYES suffered squeaky bum time before her Chelsea side sealed a comeback win.
Victory lifted the Blues to top spot and fired a warning to title rivals Arsenal and Manchester City.
The three points away at Rush Green Stadium did not come easy, with the Hammers defending well before taking the lead midway through the second half.
Boss Hayes said: We seem to like coming from a goal behind.
Thats something I have to reflect on because going a goal behind on three separate occasions this year puts a lot of pressure on a manager.
My backside got a bit tight when their goal went in. Im just pleased with the squad and the bench once again pushing the team forward.
I thought it was an unbelievable win and response from the team. We havent lost in the league. This time last year we were out of the race.
It was a good recovery from a goal down. I dont think last season our character would have got us back in this game.
This year I think thats what the difference is. Its the togetherness and the spirit of the squad.
The game was goalless until the 59th minute when West Hams Canadian sub Adriana Leon put the home side ahead with an angled strike seconds after being brought on.
Chelsea fought back when Sophie Ingle equalised in the 70th minute then three minutes later Ji So-Yun powerfully fired home before Drew Spence sealed it in injury-time.
Leon said: When we went ahead we needed to focus more on defence and give them less space.
I think we were a little lackadaisical with that. A good team like that are going to capitalise.
