Brighton and Hove Albion became Women's Premier League champions at Adams Park with a 4-2 play-off win over Northern Division winners Sporting Club Albion.
Brighton can now be promoted to Women's Super League Two, should they meet the necessary WSL licensing requirements.
They netted quickfire second-half goals through Kate Natkiel, Sophie Perry and Amy Taylor, after Natkiel had earlier cancelled out Leigh Dugmore's opener.
Karen Clough scored a late consolation, as Sporting Club stay in tier three.
The Women's FA Cup quarter-finalists, affiliated with West Bromwich Albion, had won 17 of their 22 league games in 2015-16 to win their division by four points, ahead of Preston North End Ladies.
Southern Division winners Brighton, who lost just two league games all season, terminated manager James Marrs' contract following a disciplinary hearing in April.
The Seagulls could now become only the second team to join the WSL via the promotion route, after Sheffield FC Ladies went up to WSL 2 ahead of 2016.
The WSL is expanding to 20 teams by 2017, with just one team promoted from the third tier this year and no side due to be relegated from WSL 2.
Brighton's Kate Natkiel: "It has been a hard few months, but we really rose to it and we've come together as a team and we didn't let anything get us down.
"It's amazing, I couldn't think of anything better, I couldn't ask for a better performance.
"All the fans that came to watch us, gave us their support - and I think we rose to the occasion and we gave them everything we had."
Sporting Club Albion boss Graham Abercrombie: "We created lots of chances. We put a really good side under lots of pressure and forced them into lots of errors. It was an even game for me but unfortunately the scoreline reads differently.
"We've lost a game today, that's all, we've lost one game, but this team as a group has a togetherness that's unbreakable.
"This team will go again and again and again, not just next year, but for the next 10 years."
Brighton and Hove Albion (3-5-2): Baker; Cooper, Ashton-Jones, Boswell; Perry, Barton, Young, Olding (Rowe 90), Somes (Dorey 80); Taylor (Fulgence 86), Natkiel.
Subs not used: Leitch, Wilson.
Sporting Club Albion (4-4-2): Thomas; Crossman, Conroy, Darby, Highman; Smith, Holmes, Greaves, Parnell (Clough 74); Dugmore, Cottam (Haynes 74).
Subs not used: Edmunds, Dicken, Wright.
Referee: Anthony Tankard