The editor of the South Wales Echo, the evening newspaper which covers Cardiff and the south Wales valleys, is to quit the paper, it has been announced.
No date has been set for Mr Williams' departure from the Echo
Richard Williams' employers Trinity Mirror say he will leave "to take his career in a new direction".
According to the website Hold The Front Page, the paper sells 50,422 copies Monday to Friday, a figure which is down 9.6% year-on-year.
Mr Williams, 38, has been in the post for around two years.
In August 2006, the South Wales Evening Post which is based in Swansea, overtook the South Wales Echo as the biggest selling evening newspaper in the country, according to the Audit Bureau of Circulation figures.
This trend continued in figures published in March 2007.
A spokesman for Trinity Mirror said: "We would like to thank Richard for his hard work, dedication and professionalism since taking the editor's chair in 2005 and to wish him all the best with his future plans."
The spokesman added that Mr Williams had led campaigns, overseen the revamping of the Saturday paper and the introduction of the live it! supplement.
Mr Williams, who was previously editor-in-chief at the Evening Leader in Wrexham, said it had been a "great privilege" for him to edit the Echo,
"The Echo is one of the great regional newspapers and has a very talented editorial team," he said.
No official date has been set for Mr Williams' departure and no plans to appoint a successor had been made, said the Trinity Mirror spokesman.