Her appointment comes ahead of a "major marketing campaign" as well as changes to the look and content of the Sunday tabloid due to be unveiled this weekend.
In addition to Newton's appointment, the newspaper has recruited Tony Parsons to replace comedian Frankie Boyle as a columnist and is hiring an additional 16 journalists to work exclusively on The Sun's Sunday edition.
Newton, who will report to The Sun editor David Dinsmore, began her career at The Express before joining The Sun's showbiz team where she went on to become its Los Angeles correspondent and then editor of Bizarre.
She said: "I am thrilled to be given the opportunity and the resources to take Britain's number one Sunday newspaper to an even better place.
"The Sun has a formidable reputation for exclusive, hard hitting and investigative journalism and alongside the humour and headlines, showbiz and comment, I look forward to securing The Sun firmly as the home of the best Sunday stories."
David Dinsmore said: "Victoria is ideally placed to build on the Sun's long-standing success and ensure our readers our amused, informed, provoked and championed every Sunday, as they are during the week. I am delighted to welcome her to this vital role."
The Sun on Sunday was launch in February 2012 as a replacement for the News of the World, which Rupert Murdoch closed down in the wake of the phone-hacking scandal.