Four heavyweights of world rugby will grace the Twickenham turf in an historic double header on June 22 – with a clash between South Africa and Wales followed by Barbarians versus Fiji.
Wales face the world champions before travelling to Australia for a two-Test series in July, while the Springboks host Ireland in a two-match series this summer.
The Wales-South Africa match is outside World Rugby's international window and takes place on the same day as the URC final.
South African side Stormers have featured in the past two URC finals and are currently sixth with the Bulls third, with the top eight of 16 teams reaching the play-offs. Ospreys are the highest-placed Welsh side in seventh spot.
The Principality Stadium is not available this summer because of concerts, with Taylor Swift playing at the ground on June 18 and the Foo Fighters on June 25.
Wales were beaten 52-16 by South Africa in a World Cup warm-up match in Cardiff in August.
“I'm incredibly excited about the fixture list for Wales this summer,” said Wales head coach Warren Gatland.
“To have the opportunity for our young squad to test itself against the world champions at a neutral venue is an extremely important experience. It should be a great occasion for the fans and something a bit different for them.”
South Africa beat New Zealand at Twickenham in a World Cup warm-up match in August.
“We are thrilled to return to Twickenham and we have fond memories of the warm-up Test we played against the All Blacks last year,” said South Africa head coach Rassie Erasmus.
“The atmosphere and occasion were remarkable, and we expect a similar experience in June.”
The Barbarians will be led by Kiwi coach Robbie Deans. Ben Youngs – England's most-capped male player of all time – has already been confirmed by the Baa-Baas, with a host of world stars to follow.
To book tickets visit: www.ticketmaster.co.uk/event/35005F86F7CA9A61
