The rugby football unions of England, France, Ireland, Italy, Scotland and Wales have agreed and signed a Constitution which will provide the future framework for the Six Nations Championship.
The Constitution replaces both the 1996 Regulations of the Five Nations Committee and the Five Nations Accord of the same year.
For the first time, it formally recognises the involvement of Italy in the tournament, and provides for a new structure for the pooling and sharing of income.
Chief Executive John Feehan said: "This is a very important moment for the Six Nations.
"The Constitution provides us for the first time with a commercial and organisational structure which is worthy of the greatest annual rugby tournament in the world and which is appropriate to the needs and opportunities of the professional era."
The Constitution underlines the threefold mission of the Six Nations as the stimulation of competition at the highest level; the protection, preservation and enhancement of the Championship; and the maximisation of commercial revenues.
It reconfirms the 'window' for the tournament as being February to April, provides for full sharing for Italy, and adjusts significantly the formula for the distribution of income.
Historically, income has been pooled and redistributed thus - 90% divided equally between the partners, 5% distributed according to the number of clubs in each union, and 5% each year on the basis of the Unions' performance in the Championship.
Henceforth, 75% will be divided equally, with 10% divided according to the number of clubs, and 15% allocated according to performance. A Grand Slam, for instance, would be rewarded with 5.5%.
Changes include the establishment of a limited liability company to oversee all commercial activity, the strengthening of the Committee structure, and, for the first time, the creation of the additional post of Deputy Chairman/Honorary Treasurer, to which position Bill Beaumont of England has been elected.
Six Nations chairman, Jacques Laurans, said, "The signing of a new Constitution for the Six Nations Committee is a very important moment for the Championship.
"It has enabled to build significantly on our great legacy, and yet leave behind us the temporary arrangements which were put in place at times of strife or opportunity.
"This Constitution, which has been debated exhaustively, represents the coming together in harmony of six partners. With this base, we can now move on to even greater things."