Nicknamed Stan, Ferenczi scored several crucial goals in the first season of survival in the Championship, when he netted against Stoke City and two against then relegation rivals Hull.
His 2007/2008 campaign was obstructed by injury but that didn't stop him netting five goals in the season and he played a part in the epic cup run which saw him run out at Wembley against Cardiff City in April.
Reds boss Simon Davey told the Official Website:
"It has always been a dream of Istvan's to play for the biggest club in Hungarian football and we were not prepared to stand in his way at this stage of his career.
"Istvan has been a great servant to our club and contributed a great deal to our successes in the last two seasons. He has been a major part in what we have achieved and we all wish him every success in the future".
Overall in Barnsley red, Stan scored 12 goals in 58 league appearances and captured the hearts of Reds fans for his 100% attitude and workrate.
I think I speak for all Barnsley fans across the globe when I say, thanks for the memories Stan, you were always committed to the cause and gave 100% in every game you played. Thanks Stan, and good luck.