Leeds United have signed Diogo Monteiro from Swiss side Servette FC on a three-and-a-half-year deal.
The 18-year-old made his league debut for Servette at only 16, becoming the third-youngest player to make an appearance in the Swiss Super League.
The defender has also featured for Portugal from under-15 to under-19 level.
He will join the Leeds Under-21 squad for the remainder of the season.