South African teams Cheetahs and Southern Kings will join an expanded Pro14 in time for the 2017-18 season, competition organisers confirmed on Tuesday.
The move increases the number of teams in the league, which grew out of the Celtic League and was previously known as the Pro12, from 12 to 14.
The championship will be split into two seven-team conferences, each containing two Welsh teams, two Irish teams and one club from each of Scotland, Italy and South Africa.
"The arrival of the Toyota Cheetahs and the Southern Kings marks a bold and exciting new chapter for the Guinness PRO14 as a global rugby championship," said Pro14 chief executive Martin Anayi.
"South Africa is a rugby powerhouse of over 55 million people. These teams already operate to the high standards demanded by Super Rugby and they will add to the quality of our tournament.
"The appeal of professional club rugby has never been greater and we aim to be at the forefront of the game's growth around the world."
The Cheetahs, from Bloemfontein, and the Port Elizabeth-based Kings will play their home games in South Africa.
They will only play on Saturdays and there will be five travel-free days before matches.
The Cheetahs and Kings will not be able to qualify for European competition.
The pair lost their places in the southern-hemisphere Super Rugby, which is being cut from 18 teams to 15, at the end of the current season, which ends on Saturday with the final between South Africa's Lions and New Zealanders Crusaders.
"This development is as exciting as the launch of Super Rugby itself back in 1996," said South Africa Rugby CEO Jurie Roux in a statement on the Pro14 website.
"It will not be without its challenges in aligning with a competition in a different part of the calendar and in very different playing conditions.
"But it is also a fantastic opportunity for South African rugby to widen our rugby horizons."
Conference A will feature the Ospreys, Cardiff Blues, Munster, Connacht, Glasgow, Zebre and Cheetahs.
Reigning champions Scarlets will line up alongside Dragons, Leinster, Ulster, Edinburgh, Treviso and the Southern Kings in Conference B.
Each team will play every other team in their own group home and away, in addition to one-off matches against all the teams in the other group.
Two additional rounds will guarantee the Welsh and Irish teams retain six derbies each, while the Scottish, Italian and South African teams will play each other three times.
Six teams will qualify for the end of season knock-out phase culminating in the Pro14 final.
The top three non-South African teams in each conference and the team with the next best points tally across both conferences will qualify for the Champions Cup.
The first round of the season is due to be played on the weekend of September 1-3. The fixtures have not yet been announced.