Five's chairman and chief executive Dawn Airey is to leave the channel in a shake-up of senior management, it has been announced.
Seven of the broadcaster's nine executive board directors will also leave as part of new owner Richard Desmond's changes to the station.
Plans to invest £1.5bn in the channel for programming over the next five years were also confirmed.
Desmond's Northern & Shell company bought Five Group for £104m last month.
Ms Airey will take up a senior role with Five's former owner, the RTL Group. However she will remain in her current post for several months to help run a cost-efficiency programme which, it is hoped, will return the broadcaster to profitability.
The broadaster was hit hard by the slump in advertising revenue during the economic downturn and posted an operating loss of £8.3m in 2009.
"The day Five was sold, my job was done," Ms Airey said in a statement.
"I will be returning to the RTL Group but over the next few months will remain in post with a number of my senior colleagues to facilitate the integration of Five into Northern & Shell."
The £20m cost-cutting drive is past of an "ambitious new investment plan that will see the channel go toe-to-toe with the biggest players in the TV world," a statement from the channel added.
The savings are expected to lead to between 60 and 80 other job losses, in a company of about 300 employees.
Staff will also be relocated from London's Covent Garden to the Northern & Shell premises in Lower Thames Street in the city and in the Docklands area.
Senior executives leaving include channel controller Richard Woolfe and managing director Mark White.
Five's director of digital channels and acquisitions, Jeff Ford, will take on additional responsibility for the main channel, becoming the programme director for all of the station's channels - which include Fiver and Five USA.
The station will also revert back to its original name, Channel 5. A spokesman said: "The rebrand is being done by our in-house creative team."
Richard Desmond, said: "Whilst I'm sorry to see Dawn move on, I'm thrilled that she'll be in the mix to contribute to the various exciting plans we have and oversee the acquisition and development of brilliant new content."