Amelia Ritchie, Chloe Sansom and Lucy Somes will all leave Albion, who finished second in WSL 2 last season and will now move up into Tier One of the restructured Women's Super League.
Somes graduated through the club's centre of excellence (now Regional Talent Club), and played a key role in the side's 2015/16 Women's Premier League Championship title-winning campaign.
Ritchie also came through the club's centre of excellence and enjoyed a breakthrough season in 2015/16, which saw the 19-year-old make her Wales senior debut in the 4-0 victory over Kazakhstan.
England under-20 international goalkeeper, Sansom, arrived at Albion in September last year, after leaving Reading the previous summer. She made three appearances for the club across all competitions in 2017/18.
Brighton manager Hope Powell said: “These are the difficult decisions that we knew we would have to make at the end of the season, and from my experience, it never gets any easier.
“All three players have been a pleasure to work with and both their attitude and professionalism has been exemplary during my time at the club.
"We will do all we can to offer support and provide them with the best-possible exit routes in order to pursue their careers elsewhere.
"On behalf of everyone at the club, I would like to wish Amelia, Chloe and Lucy all the very best for the future."