Chelsea beat AC Milan and Bayern Munich to land Austrian teenager Philipp Prosenik.
Prosenik is the son of former Rapid Vienna striker Christian Prosenik, who confirmed this week they had offers from Milan and Bayern before choosing the Blues.
Philipp, 16, said: "It was always my goal one day to play in England. About a month before I signed for Chelsea, they saw me at the World Cup Qualifiers, and then made contact.
"The negotiations then happened from there.
"I watched the matches against Barcelona. I'm not part of the first team but it's a crazy feeling to be joining a club which plays at such a high level."