The Serb and the Spaniard, with 46 major titles between them, will be joined by Wimbledon champion Carlos Alcaraz and Australian Open winner Jannik Sinner at the 6 Kings Slam.
World number three Daniil Medvedev and seventh-ranked Holger Rune will also play the event in Riyadh in October, oil-rich Saudi Arabia’s latest foray into the sport.
Women’s greats Chris Evert and Martina Navratilova last month criticised the flow of Saudi money into women’s tennis, as officials consider staging the end-of-season WTA Finals there.
“We did not help build women’s tennis for it to be exploited by Saudi Arabia,” read the headline for their joint opinion piece in the Washington Post.
But Tunisian star Ons Jabeur hit back, saying “people should be more informed about what’s happening in Saudi”, where a number of economic and social reforms are in progress.
Rafael Nadal, who has hinted this may be his final season, signed up as a tennis ambassador for Saudi Arabia, whose efforts to improve its international reputation through sport are often branded “sportswashing”.
As well as hosting F1 and top-level boxing, and signing a swathe of football superstars for its domestic league, Saudi Arabia will also hold a number of big events in the next decade including the 2034 World Cup.