The multimedia campaign, which launches this month and runs until 2010, will comprise TV, print and digital elements.
The activity will point users towards a microsite, where they can upload their photographs, films and stories about South Africa. The best selections will be showcased on CNN International as advertorial vignettes.
As well as TV, the ads will run in print format in CNN International Traveller magazine.
The website, which was created by London-based consultancy Brand 42, will also host a picture gallery where visitors can rate the entries, sign up for a monthly newsletter and quarterly magazine. It will be supported by a viral push and social networking activity on Facebook and Flickr.
Rani Raad, CNN's International senior vice-president of ad sales, said: "This campaign taps into the trend towards sharing experiences and sees the audience truly become part of the marketing mix, by creating the advertising themselves.
"It's a breakthrough campaign where South Africa Tourism can draw on CNN's expertise in creating completely flexible, bespoke brand concepts to reach the right audience for their business."
South African Tourism is the national tourism agency responsible for marketing the country as a preferred tourist destination. Its head-quarters is in Johannesburg, with offices in Europe, Asia, the US and Australia.