Callum Wilson scored a controversial late equaliser as Bournemouth rescued a 3-3 draw in a thrilling Premier League clash at the Vitality Stadium.
Wilson's stoppage-time header was initially ruled out for offside but was eventually given following discussion between referee Bobby Madley and his assistant.
Marko Arnautovic looked to have stolen the win for West Ham with a quickfire brace that did not cover Cherries goalkeeper Asmir Begovic in glory, and the Bosnian will have breathed a sigh of relief at Wilson's last-gasp leveller.
In a contest that swung one way and then the other, James Collins fired West Ham in front after seven minutes before goals from Dan Gosling and Nathan Ake turned the match on its head.
Bournemouth were fortunate to have 11 players on the pitch after Simon Francis caught Cheikhou Kouyate with a high boot in the first half.
The result leaves Bournemouth in the bottom three, while West Ham sit 17th.
West Ham collected their first away win of the season at Stoke City earlier this month, and captain Collins quickly had his side on the front foot.
The former Wales international shook off marker Francis to meet a corner at the front post and glance a header beyond Begovic in the Bournemouth goal.
Josh King - scorer of a hat-trick in this fixture last season - sliced wide from the centre of the box as Bournemouth squandered their chance at a swift reply, before Andre Ayew was just off target from an inviting cutback at the other end.
King was wayward once more when his next attempt came from a similar position to his first, but Adam Smith went closer by forcing Adrian into action with a dipping shot that required a touch over the crossbar.
Bournemouth eventually found the net through Gosling after Collins failed to clear his lines from a free-kick, allowing the midfielder to rifle home a finish from 12 yards.
Francis was lucky to stay on the pitch when he escaped with a yellow card after catching Kouyate with a high boot to the face shortly after the leveller, and Wilson fizzed an effort just wide early in the second half.
The turnaround was complete in the 57th minute, when a ball from deep somehow found its way to Ake in the box and the defender turned an accomplished finish beyond Adrian.
But West Ham were not done yet - Arnautovic pounced on a mistake by Begovic to pull the visitors level, with the goalkeeper having slipped on the greasy surface when dealing with a back pass.
GOALLLL!!!!!!!! pic.twitter.com/5ykrvDj3B6-- West Ham United (@WestHamUtd) December 26, 2017
Begovic could also have done better when he parried a Javier Hernandez strike into the path of Arnautovic for an 81st-minute goal that looked set to clinch the win for David Moyes' side.
However, Bournemouth were eventually awarded the draw by committee after Madley and his assistant collaborated to rule that the seemingly offside Wilson committed no offence in heading home the leveller, much to the anger of the visiting players.