The It's Always Sunny in Philadelphia star, who co-owns the club alongside fellow Hollywood actor Ryan Reynolds, took to Twitter after a nail-biting climax against Briton Ferry.
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Rebecca Pritchard scored the decisive goal with 15 minutes left that saw the match end 1-0.
The result means that Wrexham Women have been promoted from the Adran North League and will thus play in the Adran Premier, the highest tier of women's football in Wales, next term.
McElhenney tweeted: "ABSOLUTELY INCREDIBLE. CONGRATULATIONS @WrexhamAFCWomen!!!!!!!"
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The women's sport has grown in support exponentially in recent weeks and the record attendance was smashed last month when Wrexham Women faced Connah's Quay Nomads.
With Reynolds and wife Blake Lively also in attendance, 9,511 people turned up at the Racecourse Ground.
It saw the previous record readily beaten which was 5,175, for Cardiff City Women's win over Abergavenny last October.
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And the increased crowds will now watch the women play in the Adran Premier League from next season onwards.
They did so in dramatic fashion in the play-off final with just one goal to separate both sides.
It was Pritchard that landed the telling blow, who managed to get to Rosie Hughes' cross before Briton Ferry goalkeeper Courtney Young.
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Hughes nearly doubled the lead with minutes left in the contest but her effort hit the crossbar.
And in a flash, Briton Ferry had countered and only a superb stop from Wrexham keeper Delyth Morgan kept them from an incredible last-gasp equaliser.
At full-time, there were wild celebrations from the fans and players, while the coaches collapsed in a heap as they embraced.
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The men's team are also looking good to get promoted back into the EFL with Wrexham a point ahead of second-placed Notts County with three matches left. Phil Parkinson's side also have a game in hand on County.