Albion midfielder Oliver Norwood has left the club to join Championship side Sheffield United.
The 27-year-old, who made 37 appearances in Albion's promotion-winning 2016/17 campaign, will join the Blades on loan until January and the deal will then become permanent when the transfer window reopens.
Norwood spent last season on loan at Fulham and played 47 times as the Cottagers were promoted into the Premier League.
Brighton manager Chris Hughton said: “Ollie was one of our promotion-winning team in 2016/17 and will rightly be remembered as part of that historic team which took the club to the Premier League.
“He is keen to play regular senior football and this move to Sheffield United provides him that opportunity. On behalf of everyone at the club I’d like to thank Ollie for his efforts and wish him all the very best for the future.”