Hazlitt, who also previously held senior positions at Yahoo and Virgin Radio, will have a wide commercial remit at ITV when she officially joins on August 2.
Her newly created role, which unites ITV's airtime sales and online businesses, includes all responsibilities previously held by Rupert Howell, who confirmed last week that he will quit ITV at the end of July.
Hazlitt will further take on the duties of ITV's managing director of online and interactive Ben McOwen Wilson, who is also leaving the broadcaster.
She will directly manage ITV customer relations director Gary Digby and marketing director David Pemsel.
The new position was created following ITV chief executive Adam Crozier's strategic review of the broadcaster. ITV said that it signals the company's intention to more effectively exploit its commercial brands across multiple platforms.
In a statement, Crozier said that his main priority upon joining ITV was to put together a management team that could transform the firm over the next three to five years.
"That means finding the right people with the right skills and experience to create ITV's future. Fru's background in general management, her proven commercial skills and her online experience with Yahoo make her the ideal candidate for this pivotal new role," he said.
"She is renowned for her tremendous energy, her understanding of both media and technology and her ability to deliver real change and results on the ground. She will be an integral part of the engine room that will drive ITV’s future performance alongside Peter Fincham and [incoming boss of ITV Studios] Kevin Lygo.
"We already have the best television airtime sales team in the country under Gary Digby, but we need to get better at exploiting our brands fully across all platforms and reducing our reliance on a single volatile revenue stream."
Hazlitt expressed her excitement at joining an ITV team that will attempt to refocus the broadcaster as a truly multi-platform commercial operator.
"ITV has some incredibly powerful programme brands and the opportunity to properly exploit those brands across all platforms is hugely compelling," she said.
"I'm looking forward to working with Gary and the sales team to develop a wider commercial focus across all areas of the business and with the online and interactive teams to effectively leverage the content so that it has multi-platform appeal and functionality."
Also today, ITV unveiled a live simulcast service of ITV1 and ITV2 on the iPhone to launch in time for the World Cup.