PRO12 organisers have confirmed that the competition will expand to include two South African sides from the start of the 2017-18 season.
Following weeks of speculation, Celtic Rugby and the South African Rugby Union confirmed on Tuesday that the Cheetahs and Southern Kings would join the new PRO14 competition in time for the upcoming campaign.
In a joint statement the two bodies revealed that a "long-term strategic agreement" had been signed, believed to be for an initial six years.
As part of the new format the competition will be split into two conferences of seven teams, each featuring two sides from Ireland and Wales, with one each from Italy, Scotland and South Africa.
The split has been based on results from last season and will pit Munster and Connacht against Ospreys, Cardiff Blues, Glasgow Warriors, Zebre and the Cheetahs in Conference A.
Conference B consists of reigning champions Scarlets, Leinster, Ulster, Edinburgh, Treviso, Dragons and the Southern Kings. The conferences will be redrawn before the start of each season.
Each team will play 21 regular season games, consisting of home and away ties against the six sides in their conference, plus one game against each club in the other conference as well as two extra derby games.
"The agreement means that the Championship will take place across the Northern and Southern Hemispheres and marks the first phase of expansion as the Guinness PRO14 becomes a truly global tournament," the joint statement read.
"This move will contribute to the drive for ever higher standards that we demand across the tournament and provide greater resources to our clubs who will compete in the most testing environment the championship has ever created.
"We can also reassure supporters across the championship that all current home and away derby games have been protected -- these fixtures are sacrosanct to the tournament and those tribal rivalries are just one element of what makes the Guinness PRO14 so special."
Details of fixtures for the upcoming season have not yet been released.
The Cheetahs and Southern Kings join the PRO14 having been dropped by Super Rugby following its decision to slash its competition from 18 clubs to 15. It is expected they will play their away games in blocks to cut down on travel time.