People flying into Britain for the London 2012 Games will be able to spot champion heptathlete Jessica Ennis from the air declaring "Welcome to our turf".
A 53m by 75m image of the Sheffield star has been painted on to Thornbury Playing Fields about three miles from Heathrow Airport. It is bigger than 15 tennis courts and 193 London buses.
Ennis, one of the favourites in a tight race for heptathlon gold at the Olympics, said: "I'm thrilled to be the first face that people will see arriving into the UK for the London 2012 Games. I hope it brings excitement to homecoming Brits, and reminds international athletes that we're ready and prepared."
She added: "We have the most dedicated fans in the world, who will get behind us every step of the way to give us a home advantage."
British Airways, a London 2012 sponsor, said it created the image to welcome home Team GB and ParalympicsGB supporters and remind athletes from overseas that only one country has home advantage. It also has the Twitter hashtag £HomeAdvantage.
It took two days and more than 600 litres of red, white and blue weatherproof paint for painters to complete the project. It will be on show for five weeks to July 17 and retouched at intervals to keep it fresh.
US rower Kate Johnson, the 2004 Olympic silver medallist in the women's eight, said: "As an athlete at the Athens Games in 2004, one of my strongest memories was seeing the city for the first time as we flew in, because that's when the reality kicked in.
"It's an exciting and anxious moment for athletes, and I expect they will be amused and a perhaps a little unsettled to see such a bold message as they arrive to the UK."
Heathrow will be the main flight hub for the Games with millions of passengers set to stop off there.
Airports owner BAA estimate that 80% of all Games visitors will pass through the airport on its busiest days. These include July 16 as the peak day for athlete arrivals and July 26 peak day for arrival of sponsors and media.