The addition of South African rugby teams the Southern Kings and Cheetahs will see the Pro12 expanded and split into two conferences.
From next season the new Pro14 tournament will be made up of two conferences of seven teams — two Welsh, two Irish and one team from each of Scotland, Italy and South Africa.
The new-look format has been described as just the "first phase of expansion as the Guinness Pro14 becomes a truly global tournament," in a joint-statement from Celtic Rugby and the South African Rugby Union.
Last season's results have formed the basis of the two conferences. Runners-up Munster, Connacht, Ospreys, Cardiff Blues, Glasgow, Zebre and the Cheetahs form Conference A. Conference B is made up of reigning champions Scarlets, Dragons, Leinster, Ulster, Edinburgh, Benetton and Southern Kings.
The top three sides from each conference will progress into a knock-our round for the championship, after 21 regular-season games made up of 12 home and away fixtures against teams in the same conference, seven home and away games against teams in the opposite conference and two remaining derbies.
"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 the competition's chief executive Martin Anayi.
"As a country, South Africa is a rugby powerhouse of over 55m people. These teams already operate to the high standards demanded by Super Rugby and they will add to the quality of our tournament.
"These are bold steps but the encouragement from our shareholder unions, our sponsors, our broadcasters and World Rugby has shown that there is an appetite for innovation, fresh stories and new rivalries.
"The new tournament structure will also provide more teams with the opportunity to reach the Guinness Pro14 final series and that is fantastic news for our players, coaches and fans."
The addition of the two South African sides is estimated to bring £6m in additional revenue to the tournament and is rumoured to be the first part of an expansion that could stretch to North America in the future.
Cheetahs and the Southern Kings have left southern hemisphere competition Super Rugby, who are cutting down from 18 teams to 15 and from four conferences next season.