Lee Guem-min has left Albion ahead of the transfer deadline and linked up with two of her former bosses.
Th South Korea international forward has signed a two-year contract at Championship outfit Birmingham City, who are coached by Amy Merrick.
She made 96 appearances for the Seagulls in all competitions across four years, having initially signed for Hope Powell, who is now technical director at Birmingham.
Lee was a popular figure among Albion players and fans and her 13 goals for the club included a famous late winner away to her previous club Manchester City last season.
Birmingham have paid Albion an undisclosed fee.
The move continued a busy deadline day which has also seen China defender Li Mengwen go to West Ham on loan.
Grace McEwen and Lily Dent signed loans at Portsmouth while young Arsenal striker Michelle Agyemang has signed a similar deal with the Seagulls.
Only Kayleigh Green, Aileen Whelan and Victoria Williams have played more games than Lee for Albion in the WSL.
Head coach Dario Vidosic said: “Lee has been a great servant of the club in the last four years and a popular member of the squad.
“I enjoyed our brief time working together and I’m sure she will relish this new challenge. We wish her all the best for the next stage of her career.”
Birmingham, once one of the strongest women’s teams in the country, are keen to get back to the top flight and opened the league season by beating Sunderland 5-0.
Lee, 30, said: "I’ve worked with Amy at Brighton and I’m really happy to work with her again. I can’t wait to start playing for Birmingham City."
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