Sporting sign Elias from Atletico
The 26-year-old has signed a contract until 2016, Sporting added in a statement.
Elias joined Atletico in December last year from Corinthians and made 15 appearances, scoring two goals for the La Liga club.
He got his first Brazil call-up in September 2010 and has since played seven times, including against Argentina in July's Copa America. He is in Brazil coach Mano Menezes's squad for Monday's friendly with Ghana in London.
It is a record buy for Sporting, eclipsing the seven million euros spent on Chilean midfielder Rodrigo Tello in 2001.
Elias is the club's 16th signing of the transfer window as they conduct a major overhaul of the squad under new coach Domingos Paciencia in a bid to improve on last season when they finished 36 points behind champions Porto.
Despite the changes they have made a lacklustre start to the new campaign with just two points from their first three games.