Ms Brooks will be in charge of the Sun, which she used to edit, and the Times and Sunday Times. She also edited the News of the World, but this was closed in the midst of the phone hacking scandal.
She said: “I am delighted to return to News UK. It is a privilege to be back amongst the most talented journalists and executives in the business.”
Ms Brooks left News UK’s predecessor, News International, four years ago, and her return sparked criticism from Labour and the campaigning organisation Hacked Off.
Shadow culture secretary Chris Bryant, who was a victim of News of the World phone hacking, said her appointment was “ludicrously premature”, adding: “Rupert Murdoch has just stuck two fingers up to the British public and the thousands of people whose phones were hacked by News International.
“Hundreds of ordinary journalists lost their jobs when Mr Murdoch closed the News of the World, but it seems Rebekah Brooks is to get very special treatment.”
But Robert Thomson, chief executive of parent company News Corp, said: “Her expertise, excellence and leadership will be crucial as we work to extend our relationship with readers and advertisers, and develop our digital platforms to take full advantage of our brilliant journalism.”
Evan Harris, joint executive director of Hacked Off, said: “This could only happen in a dynastic company where normal rules of corporate governance simply do not apply.”
Rebekah Brooks was cleared of all charges following the 138-day phone hacking trial at the Old Bailey, as was Stuart Kuttner, former managing editor of the Sunday tabloid.
But Andy Coulson, another former editor of the newspaper who went on to become David Cameron’s director of communications, was convicted and handed an 18-month prison sentence.
Former Daily Telegraph editor Tony Gallagher becomes editor of the Sun, Britain’s biggest selling daily newspaper.