The 19-year-old forward, who has made one first-team appearance for Chelsea, spent last season on loan at Dutch club Vitesse Arnhem.
Brown joined Chelsea from West Bromwich Albion in 2013, shortly after he had made his senior debut for the Baggies at the age of 16.
That made him the second-youngest player to appear in the Premier League.
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Chelsea youngster Izzy Brown has joined Championship side Rotherham United on a season-long loan.