
She replaces Dan Brooke, who left the company in January.
Forbes, who takes up the role in January 2010, is currently senior vice president and general manager, Turner Broadcasting System, UK/Ireland.
She will be responsible for Discovery's UK/Ireland business - the single largest market for Discovery outside the US. Discovery Networks UK is one of four regional business units managed within Discovery Networks International.
She will report to Greg Ricca, chief executive and president of Discovery Networks International, and manage all commercial and channel activities in connection with Discovery's UK business. The UK business currently consists of 12 pay TV brands.
At Turner, Forbes oversees all aspects of the Turner business in the UK and Ireland, an entertainment network of seven channels including Cartoon Network, Boomerang and Turner Classic Movies.
Her remit covers commercial and network functions including ad sales, sponsorships, programming, on-air, operations, research, business development, marketing and communications.
She has spent 14 years working at Turner in a variety of commercial roles including senior vice president of advertising sales, sponsorship and promotions for EMEA as well as General Manager for the Nordic/Central and Eastern Europe and EMA regions.
Prior to joining Turner, Forbes worked at Media Audits, a media consultancy that advises UK advertisers on media strategy and at Young and Rubicam Media in Europe.