Mitroglou, 25, was the top scorer in this season's Greek Super League with 14 goals and arrives for an undisclosed fee reported to be in the region of �12.5 million ($20.6 million, 15.3 million euros).

"Fulham Football Club is delighted to announce the signing of Greece international Konstantinos Mitroglou on a four-and-a-half-year deal for an undisclosed fee, seeing the player at Craven Cottage until the summer of 2018," read a statement on the Fulham website.

Mitroglou began his professional career with Borussia Moenchengladbach in Germany before joining Olympiakos in 2007. He went on to make 148 appearances for the Greek heavyweights, scoring 62 goals.

Earlier this season he became the first Greek player to score a Champions League hat-trick when he claimed all three goals in Olympiakos's 3-0 group-phase success away to Belgian side Anderlecht.

He has scored eight goals in 28 international appearances, notably netting three times as Greece overcame Romania in a two-legged World Cup qualifying play-off in November.

Mitroglou will be expected to spearhead Fulham's attempt to avoid relegation from the Premier League.

Manager Rene Meulensteen's side have lost 12 of their last 15 games and are currently second from bottom in the English top flight.