By SABC Sport
1st September 2023
The 20-year-old Spain international made 36 LaLiga appearances last season for Barcelona as they went on to win the title.
"This is a great deal for all of us," Brighton head coach Roberto De Zerbi said on the Premier League club's website.
"I am sure Ansu will help us to reach a new target and we can help him get back at the level he deserves to be."
Fati came through the Barcelona academy, making his senior debut in August 2019 and later became the club's youngest goalscorer in both LaLiga and the Champions League.
Brighton technical director David Weir said: "Ansu is one of the most highly-rated young players in the world and arrives with an impressive amount of experience both domestically and in European competition, despite his age.
"This season is the biggest in the club's history and we're really happy that a player of Ansu's quality is going to be part of it."