Alexandra Shulman is stepping down as editor-in-chief of British Vogue after more than 25 years in the role.
The magazine editor, who was recently seen in an eye-opening BBC documentary about the fashion bible, intends to leave this summer.
"Although I have had months to acclimatise to the idea of leaving Vogue, it hasn't made the moment of announcing this any less sad," she said.
"I have been incredibly privileged to have been able to look after such a great magazine for so long and even more to have worked with so many people over those years who have made the experience so interesting and rich."
Shulman said it was a hard to decision to quit the magazine "that I love".
"It was difficult to decide to leave but 25 years is a very long time and I am tremendously excited that I will now look forward into a different future," she said.
"But I know that nothing will be quite like the years I have spent at Vogue."
Viewers of the recent BBC programme saw Shulman seal a coup for the magazine by landing the Duchess of Cambridge as the title's cover girl, celebrating the 100th edition of British Vogue - while embarking on an elaborate ploy to keep the deal secret from acclaimed film-maker Richard Macer.
The fly-on-the-wall documentary also saw Shulman ditch her April cover star, supermodel Kate Moss, and replace her with Rihanna to prevent US Vogue editor-in-chief Anna Wintour getting an exclusive on the singer.
Nicholas Coleridge, managing director of Conde Nast Britain, paid tribute to the magazine editor.
"Alex has been the longest-serving and most successful editor of Vogue in its 100-year history," he said.
"She has edited the title for a quarter of its existence, through its period of highest ever circulation, and its simultaneous transformation into a global digital brand.
"She has been the towering figure of the British fashion press throughout her tenure: a superb journalist and editor, who understands and exemplifies every quality."
He added: "Imaginative, hard-working, perceptive and a brilliant leader, Alex is also a valued friend to so many of us. It is impossible to sufficiently express the contribution she has made to Vogue, to Conde Nast and to the British fashion industry."
Shulman's successor has not been named.
She said she had seen the British fashion industry "expand and flourish" but wanted to "experience a different life".
"I have edited British Vogue for 25 years almost to the day, and to have steered it during our spectacular centenary has been one of the greatest privileges," she said.
"It has been very hard to find a rational reason to leave what is unquestionably a fascinating and rewarding role, but last autumn I realised that I very much wanted to experience a different life and look forward to a future separate to Vogue."
Recent landmark editions of the magazine included featuring "real" women, instead of models, on its fashion pages in the November issue.
Despite her job, Shulman does not appear to be obsessed with her looks.
She once told The Guardian: "There was a newspaper piece which was kind of a round-up of all the editors of Vogue, and it was like the Russian one and the Italian one - and the description of me was 'chain-smoking 50-year-old Toyota-driving divorcee', and I thought, 'Hmm, bit too much reality, actually'. I could have done with a bit more 'cool ice-maiden'."