WASHINGTON — He’s been photographed kite-surfing with Richard Branson off Necker Island, relaxing on David Geffen’s yacht in French Polynesia with Bruce Springsteen and Oprah Winfrey, river-rafting with his family in Bali and posing with a celebrity chef in Tuscany.

To those who have paid only casual attention to former President Barack Obama’s foreign travels since he left the White House in January 2017, it can seem as if Mr. Obama has been on an extended vacation of the kind only the very rich can afford.

But the former president has also met quietly with groups of young people in New Zealand, Brazil, Indonesia and Singapore, as well as paying calls on foreign leaders, including Xi Jinping of China, Emmanuel Macron of France, Justin Trudeau of Canada and Malcolm Turnbull of Australia.

Now, Mr. Obama is inaugurating his most significant international project as an ex-president, with an announcement on Monday that the Obama Foundation plans to convene 200 young people this July in Johannesburg for five days of meetings, workshops and technical training.