Jeremy Blood has quit his job as managing director of Heineken UK with immediate effect.
His departure is for "personal reasons", although no details were given.
Blood was little more than a year into the job. He was appointed head of Heineken's UK operation - effectively Scottish & Newcastle as was - in April 2008.
In a statement Heineken said: "A successor to Jeremy will be announced shortly. In the interim, the existing management team will run the business on a day-to-day basis, reporting directly to Didier Debrosse, Heineken's Regional President, Western Europe, who will assume executive management of the company.
Debrosse said: "S&NUK is making good progress in the delivery of its plans. However, for personal reasons, Jeremy has decided to leave the business.
"I would like to thank him for his significant contribution to building both the company and its brand portfolio over the last 20 years and for his work over the last 12 months to integrate Scottish & Newcastle and Heineken UK.
"We wish him well for the future. S&NUK has a very strong and experienced management team and excellent employees, who will respond professionally and will remain focused on developing our UK business."