Although the Seagulls have withheld the finances involved in the transfer, Igor is believed to have cost around €20 million.
The 25-year-old Brazilian defender has signed a four-year contract with Brighton keeping him at the Amex Stadium until 2027.
He becomes Brighton’s fifth acquisition of the summer transfer window following the arrivals of Joao Pedro, Mahmoud Dahoud, James Milner and Bart Verbruggen.
Manager Roberto De Zerbi said: “Igor is another important player who can help us in a crucial position within the team – where the play starts.”
Igor will reportedly link up with his new teammates next week when they return from the pre-season Premier League Summer Series in the United States.
The centre-back is expected to replace Levi Colwill at the heart of the Brighton defence after the Englishman returned to Chelsea following the expiration of his loan contract.
The 20-year-old was a crucial part of De Zerbi’s side last season and played a prominent role in their historic European qualification.
The Seagulls have been keen to retain his services permanently and have already seen a bid rejected by Chelsea, who are adamant their academy graduate is not for sale.
Colwill, who has received high praise from Chelsea manager Mauricio Pochettino, is expected to be part of the Blues squad this season.
Igor’s arrival at Brighton could signal the end of their interest in the youngster, but the Seagulls also have an ace up their sleeve.
Chelsea are interested in signing highly-rated Brighton defensive midfielder Moises Caicedo who has emerged as a primary target for the Blues following a string of impressive performances.
However, Brighton are playing hardball over his valuation, insisting that Chelsea use Colwill as part of a player-plus-cash deal to sign Caicedo.
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