Chelsea have continued their acquisitions in the January transfer window, bringing in Andrey Santos from Brazilian club Vasco da Gama.
The 18-year-old midfielder joins Graham Potter's side and becomes Chelsea's third signing of the window following the arrivals of Benoit Badiashile and David Datro Fofana from Monaco and Molde, respectively.
"It’s a very big opportunity for me," Santos told the club's official website.
"This is a big club playing in big competitions like the Premier League so I am very excited.
"The players here are so good and I am very happy to be here."
So far this season, Santos has played 33 times in Brazil's Serie B, and scored eight times.
He is yet to be capped by the national side, but has featured at youth level, playing for the nation's U-16, U-18 and U-20 sides.
Santos could make his Premier League debut at Fulham on 12 January.