The promotion follows White's recent six-month period as interim chief executive between the departure of Jane Lighting in May and the arrival of Dawn Airey last week.
During the period he oversaw a number of key projects, including a complete refresh of Five's on and off air identity.
Airey, Five's chair and chief executive, said: "Mark has made a phenomenal contribution to Five over the last decade and more, and I am pleased to be able to formalise his position as my right-hand man.
"In his new role as managing director he will work closely with me in restructuring and revitalising Five."
White said: "Five is full of talented people and I'm thrilled to be given the chance to manage across the business ensuring we maximise every ounce of potential in the company."
White joined Five in 1996 as sales controller, becoming deputy sales director in 2000 and then executive director of sales in 2004, overseeing the launch of the broadcaster's digital channels, Five US and Five Life, in 2006.
He is a director of Thinkbox, the chairman of Clearcast, as well as representing Five on numerous industry committees.
Prior to Five, White worked in a variety of sales roles at Thames TV and was part of the launch team behind UK Gold.
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