Roger Alton is to step down as editor of The Observer at the end of the year and will be succeeded by John Mulholland, who is currently deputy editor.
Alton joined The Observer from the Guardian, where he spent more than 20 years in a number of roles including arts editor, features editor, editor of Weekend magazine, and assistant editor.
Alton has been the Sunday paper's editor for nearly ten years, presiding over the introduction of the award-winning monthly Sport, Food, Music, and Woman magazines, and the successful move to the Berliner format in 2006.
Earlier this year, The Observer won Newspaper of the Year at the British Press Awards.
Alton said: 'It has been an immense privilege to edit The Observer and work with such a brilliant team. For the best part of ten years, this has been the time of my life. The Observer is in fantastic shape, editorially and commercially, and this is the right time for me now to be handing over to John.
"I am absolutely thrilled at his appointment - he's a fabulous journalist and a dear friend I would trust with my life. John cares passionately about The Observer, and has a clear vision and ambition for its print and digital future. The paper is in very safe hands.'
Liz Forgan, chair of The Scott Trust, owner of the Observer and Guardian newspapers, said: 'We are very grateful to Roger for the passion and commitment he has brought to The Observer and the Guardian over the last 30 years. The award of Newspaper of the Year was a fitting tribute to an inspiring editorship.
'John Mulholland is an outstanding journalist and the Scott Trust is delighted he will become The Observer's next Editor. He played a key role in The Observer's successful move to the Berliner format, developed and launched the stable of award-winning monthly magazines, and is uniquely placed to lead the paper into an era of digital publishing.'
Mulholland, 44, has been a deputy editor of The Observer since 1998. He has been reponsible for the paper's features output, including magazines and the sport, travel and culture sections.
He is a former media editor of the Guardian and was educated at Dublin City University and California State University, Sacramento.