Sunderland have completed the signing of Greece teenager Charis Mavrias from Panathinaikos for an undisclosed fee, thought to be around £2.5m.
The 19-year-old winger, who has won two caps with Greece, has agreed a three-year deal with the Black Caps and been assigned the number 35 in Paolo Di Canio's squad.
Mavrias came up through the youth ranks at Panathinaikos and in 2010 became the second-youngest player to play in the Champions League - at the age of 16 years and eight months.
In total he has made 70 domestic and European appearances for the Greek club, scoring six goals.
Aside from his two full international appearances, Mavrias has also been capped at under-17, under-19 and under-21 level.