Pye joined Cheil as the managing director in 2011 and helped the agency pick up business from Coca-Cola, Absolut, Pernod Ricard and Descente, moving away from being a Samsung-based business.
Staff at Cheil were informed of Pye's departure this afternoon. His last day at the agency will be 31 December.
He took on his current role in 2013 and oversaw the shop’s move to Southwark.
Before this he was a managing partner and business development director at Ogilvy & Mather between 2001 and 2011.
He was an account director at Partners BDDH for two years, and began his career at Lowe Howard-Spink in 1994.
Paul Hammersley, the group chief executive at Cheil UK, said: "Matt has played an huge part in helping transform Cheil to the agency it is today and I’d like to thank him for that.
"While we’ll miss him, we look forward to carrying on his good work."
Pye said he intends to take a short break before looking for a new challenge. He said: "I've had a wonderful time and hopefully I've left the agency in a far better position than when I arrived.
"It's time for the next chapter and, with Paul at the helm, I'm certain the future is bright."