Sources added that Tottenham were also interested in a deal but Ansu will move to the Amex Stadium for the rest of the campaign. There is no option for a permanent deal, Barcelona said in a statement.
It marks a dramatic turnaround from Fati, who has previously been reluctant to leave the Catalan club this summer despite pressure from elsewhere.
Barca, his agent, Jorge Mendes, and his father, Bori, have all been pushing for him to spend a year elsewhere in order to play regular football.
After bursting onto the scene as a 16-year-old in 2019, he missed almost two years of football between 2020 and 2022 due to various knee and hamstring problems.
Brighton boss Roberto De Zerbi said in a statement: “This is a great deal for all of us. 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.”
He remained fit last season, making 51 appearances, the majority off the bench, and scoring 10 goals, but he was frustrated by a lack of starts.
That led to his father, Bori, calling for him to quit the club earlier this year and saying he was annoyed by the way Barça were treating Fati, who inherited the No.10 shirt from Lionel Messi.
Ansu has a contract with Barca until 2027 and a €1 billion release clause.
“We are delighted to bring Ansu to the club. He 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,” Brighton technical director David Weir said.
“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. We will give him the opportunity to embed himself in the squad and to get used to working with Roberto, but naturally we’re excited to see him in a Brighton shirt.”
“I’m very, very happy to be here,” Lenglet told Villa’s website. “It’s a real pleasure. I played against them with Tottenham and it was really, really difficult to play against Aston Villa.
“I spoke with the manager [Unai Emery] and [sporting director] Monchi during the summer and I’m very excited.
“It was important for me to go to a club with an important manager. We can see since [Emery] started with Villa, the team is going through to the high, top level.”
Sources have told ESPN the club are optimistic of being able to finalise a deal for Manchester City right-back Cancelo, while their push to sign Felix is likely to go to the wire.