"These new club competitions will create top quality sporting drama for our supporters and commercial partners across Europe," said Mark McCafferty, Premiership Rugby's chief executive.
"They deliver a stronger playing format for everyone.
“We are now entering a new phase of growth in the club game and, alongside the three professional leagues, we're confident that the new competitions will go from strength to strength, as well as incorporate new markets over time."
The new formats are based on key principles which have been consistent throughout the negotiations:
Qualification on merit
Strengthening of both competitions
Expansion into new markets
Fair financial distributions.
McCafferty added: "This is an historic day for European club rugby. The parties have worked hard to get to this point and the uncertainty is now over. However, there is little time to reflect as we have a great deal still to do to ensure both competitions fulfil their ultimate potential.
“Clubs in all three leagues are now battling for qualification and it is only just over five weeks until the play-off for the final place in next season's European Rugby Champions Cup. There are exciting times ahead for supporters."