The 21-year-old Brazilian made his league debut for Flamengo last year but was loaned to Santos at the start of the current season, which began on April 27.
"Olympique Lyonnais is very pleased to announce an agreement with the Brazilian club Flamengo to bring the promising young Brazilian midfielder Jean Lucas de Souza Oliveira to Lyon," the French club said in a statement.
"The amount of the transfer is eight million euros, plus a percentage of a potential future transfer. Jean Lucas has signed a five-year contract with Olympique Lyonnais."
Earlier this month Lyon sold French left back Ferland Mendy to Real Madrid for 48 million euros.
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(Reporting by Reporting by Sudip Kar-Gupta and Pawel Goraj; additional reporting by; Simon Jennings in Bengaluru; Editing by Ken Ferris)
