Phil Harrison will resign as president of SCE Worldwide Studios on 29th February 2008, Sony has just announced.
SCEI president and CEO Kaz Hirai will assume his responsibilities in addition to his current duties.
No reason has been given for Harrison's departure, and Sony has said it will make no further statements.
Harrison, one of the most recognisable faces in the games industry, has "made a tremendous contribution" to Sony since joining in 1992, the company said.
"As one of the founding members of SCE, Phil played a key role in the development and growth of the PlayStation business and our industry," Kaz Hirai said.
"It is sad to see him departing from SCE, but I wish to express my gratitude for his many invaluable contributions and also wish Phil the very best of luck in his future endeavours."
Harrison himself said: "The past 15 years at Sony Computer Entertainment has been the defining journey of my life so far. I am grateful to all the PlayStation family for their incredible support, guidance and friendship.
"It has been a privilege to serve as part of the team and be inspired by them on a daily basis. I am so proud of everything PlayStation has achieved and will continue to support its future in every way I can."
No word yet on where Harrison is going, or whether Sony plans to replace him or if Hirai will continue doing both jobs indefinitely.