The development had been well trailed but marks a major expansion to 14 sides and becomes the first cross-hemisphere club competition in the sport.
It is understood that the South Africans, who have lost their Super Rugby status, will join on a six-year deal which will be formally announced in due course. The decision was made at a Pro12 board meeting in Dublin yesterday.
The now Pro14 has grown out of the Welsh-Scottish League which was launched in 1999. The four Irish provinces joined in 2001, with Italian clubs added in 2010. Glasgow Warriors became the first Scottish side to win the title in 2015.
The Pro14 will be split into two conferences of seven teams, with Glasgow and Edinburgh in different sections. Each conference will have one South African team, one Italian and two each from Wales and Ireland.
The winners of each conference will qualify for the semi-finals, with the second and third placed teams playing off for a place in the last four.
It is expected that the development will inject around £6m from the South African into the current £12m turnover as the league looks to compete with the cash rich English and French leagues.
The Port Elizabeth-based Kings and Bloemfontein-based Cheetahs were cut from Super Rugby a week past Friday.
Kings scrum-half Rudi van Rooyen told the BBC last week that it was something the players were relishing. “A lot of the players at South African teams would prefer playing in the Pro12,” said van Rooyen.
“Most of the guys are really excited to play in the northern hemisphere – it’s a new challenge, a new type of game, playing new opposition that you don’t know at all.
“Most of the South Africans want to earn their pounds or their euros and I think playing in Europe, playing against Munster or Ulster, the big teams from Ireland or Scotland or Wales can certainly put your foot in the door a bit.”
The Cheetahs were only added to Super Rugby in 2006 along with Australian side Western Force. Their best finish was sixth in 2013.
The Kings were created in 2009 for the Lions tour and entered Super Rugby in 2013. Former Edinburgh coach Alan Solomons led them from 2009-2012.
Meanwhile, Scotland will play in front of two capacity crowds in the forthcoming Autumn Tests at BT Murrayfield for the first time in history.
The national team’s third Test against Australia (Saturday 25 November, kick-off 2:30pm) was confirmed as a sell-out yesterday – a first for the fixture, some four months out from the game – following hot on the heels of the second Test against New Zealand, which became the fastest-selling autumn
Test on record earlier this month.
Tickets are still available for the opening autumn Test against Samoa on Saturday 11 November (kick-off 2:30pm).
That match will be Gregor Townsend’s first home game as head coach and boasts a ‘Kids for £1’ offer, where under-12s attend for £1 when accompanied by an adult buying a Bronze or Silver category ticket (£15).
Townsend said: “The Scotland squad and management are hugely grateful for the outstanding and historic backing we have received from our supporters.
“It means a huge amount to everyone involved to play in front of a packed house at BT Murrayfield and we’re looking forward to getting back out there this November, first against Samoa, before taking on New Zealand and Australia.”
Further details about the waiting list for possible future release of tickets can be found at www.scottishrugby.org/autumn-tests-2017-waiting-list