British Vogue editor Alexandra Shulman is to step down as editor-in-chief after more than 25 years in post.
Ms Shulman will leave in the summer. Her successor has not yet been named.
It was “hard to find a rational reason to leave” but she “wanted to experience a different life”, she said.
Nicholas Coleridge, managing director of the magazine’s publisher Condé Nast, said: “Alex has been the longest-serving and most successful editor of Vogue in its 100 year history.”
Ms Shulman said steering Vogue during its “spectacular centenary” in 2016 had been “one of the greatest privileges” of her role.
“I have worked with an unparalleled collection of talent both inside and outside the magazine and have been lucky enough to see both Vogue and the British fashion industry expand and flourish,” Shulman 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.
She said her career at Condé Nast had been “everything I could have wished of it” and she thanked Mr Coleridge and the chairman and chief executive Jonathan Newhouse for “giving me so many opportunities, trusting me to take care of the precious cargo that is Vogue, and allowing me the freedom to do the job exactly how I wanted”.
Mr Coleridge noted she had edited Vogue for a quarter of its existence, through its highest-ever circulation, as it changed to a 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. Imaginative, hard-working, perceptive and a brilliant leader,” he said.
She was a valued friend, he said, and it was “impossible” to express the contribution she had made to the magazine.