The `Angels` hitmaker - who recently rejoined Take That - will top the bill at a one-off concert next month, which will take place at the Twickenham rugby stadium in London, to raise money for the British Armed Forces in Afghanistan and Iraq.
Other acts confirmed include James Blunt - who is a former British Army captain - Alexandra Burke and Pixie Lott, while comedians Jason Manford, Michael McIntyre and Jack Dee will introduce the artists.
Robbie said: "I am honoured to be a part of this show and to help draw attention to the amazing job done by our servicemen and women throughout the world. Their dedication to our country is phenomenal and we are all so proud of them."
Around 60,000 fans and troops will attend the concert which is being organised by The Who frontman Roger Daltrey and promoters Live Nation
The guests of honour will include injured service personnel and their carers who will receive free tickets as a small `thank you` for the sacrifices they have made for the UK.
The public are also able to purchase one of 1,000 extra tickets to treat a member of the Armed Forces to the concert.
All proceeds go straight to Help for Heroes and tickets go on sale tomorrow (04.08.10) at www.livenation.co.uk, www.heroesconcert.com and www.ticketmaster.co.uk.