The three Celtic Unions have unanimously agreed to the introduction of two new Italian super sides and the four-year agreement will see Benetton Treviso and Aironi Rugby competing against defending champions Munster and the other nine Celtic teams on a home and away basis.
Benetton Treviso will have their headquarters at Stadio Comunale di Monigo while Aironi, who will be based at Stadio Luigi Zaffanella, will involve various clubs from the Lombardia and Emilia-Romagna regions.
The move to welcome Italian sides comes at the end of a year-long review of the viability of expanding the tournament, the detailed analysis and due diligence undertaken by the sports consultancy arm of Deloittes and focusing on the basis of long term financial capacity to support the teams and commit to the league.
David Jordan, Director of Celtic Rugby, said: "This is another massive step forward for the Magners League and follows the decision to go to a top four Play-Off system to determine our champion team.
"As well as providing more fixtures for the teams already involved this will also bring both a major cash injection into the competition and greater exposure across Europe.
"The implementation of the Plays-Offs and the Magners League Grand Final this season has already seen a marked improvement in the competitiveness of the League and the arrival of two Italian teams will provide another boost to the competition.
"Operationally it will present new challenges, as well as opportunities, but by introducing Italy into the Celtic fold it will also dramatically broaden the appeal of our product.
"It is anticipated that the Italian super clubs will be largely made up of Italian internationals of full, A and under 20 levels, with a sprinkling of top class overseas players set to provide further extra strength and spice to the tournament."
Giancarlo Dondi, President of Federazione Italiana Rugby (FIR), said: "I am very pleased that, after months of intense negotiations, an agreement that will see two Italian teams join the Magners League at the start of next season has been reached.
"I would like to thank the Board of Celtic Rugby, in particular President John Hussey and Director David Jordan, for the support given in recent months.
"At the same time, I would like to thank Amerino Zatta, the President of Benetton Treviso, and Silvano Melegari, President of Aironi Rugby, who supported me throughout the negotiation period.
"I am sure that the Magners League will bring benefits to all Italian rugby and will have a positive impact on the competitiveness of our national team.