The Blues have confirmed that Stoch is to join Turkish club Fenerbahce on a four-year deal for an undisclosed fee.
Stoch's departure follows yesterday's confirmation that Joe Cole, Juliano Belletti and Michael Ballack will all leave when their contracts expire at the end of the month.
Stoch joined Chelsea as a 16-year-old in the summer of 2006 and signed professional terms a year later.
Playing as a second striker or out wide in a front three, he was the youth team's top scorer in the 2006/07 campaign with nine goals from 20 starts and six substitute appearances, and the next season was an FA Youth Cup ever-present in the run to the 2008 final.
During the 2008/09 campaign the young Slovakian made his international and club debut, the latter when coming on as a sub against Arsenal in November.
He next appeared against Stoke in the new year and played his part in a dramatic last-minute winner.
In 2009/10 he went on loan to FC Twente, managed by Steve McClaren, and the club won its first Dutch championship with Stoch scoring 12 goals in 44 starts.
He made five substitute appearances for Chelsea's first team but failed to score.
The 20-year-old will be representing Slovakia at the World Cup and a spokesperson for Chelsea said: "We would like to thank him for his contribution to the club and wish him well in his future career."