
Poppy will front the charity's new microsite and virtual world called Legion Live, which will be launched in early November.
Her character is 32 and her brother and grandfather have served in the armed forces. She will write blogs, leave comments in chat forums and post messages on social networking sites, intended to engage with users aged between 25 and 45.
The charity hopes Legion Live will attract 150,000 users over the next three years.
Separately, The Royal British Legion is also launching a sobering poster campaign to support this year's poppy appeal, focusing on the Afghan generation of the armed forces and their families.
The national activity, which has been created by The Gate Worldwide, will roll out on 19 October and run for three weeks. It will encompass sites including London Underground as well as roadsides and digital screens.
The four poster variations feature real people who have been affected by the war in Afghanistan. One features a widow with her son and photo of her husband, lost to an explosive device. Another ad features a Royal Marine who lost his legs when his vehicle struck a mine. A third shows an image of troops in active services, while the final one, for the first time, shows a casket being repatriated.
The outdoor work will be backed by online activity including banner ads.