From 2019 the championship will be known as the Guinness Six Nations.
Diageo, which owns the stout brand, has signed a six year deal, a move which "considerably strengthens" Guinness' commitment to rugby. The brand is already the headline sponsor of the Guinness PRO14, and partnerships with the four Home Unions and leading European clubs Leinster and Munster.
"The new partnership with Rugby's Greatest Championship cements the Guinness brand's position as one of the game's biggest supporters," said Diageo president for Europe, Turkey and India, John Kennedy.
"We are really looking forward to the start of the Guinness Six Nations in February 2019. Working with the Six Nations, we want to enhance both the Championship and the fan experience whilst using the partnership to encourage the adult fans watching, or attending, the games to drink responsibly."
The Six Nations is one of the world's best attended sports events and regularly attracts record TV and online audiences in the UK, France, Ireland, Italy and all over the world.
Diageo have pledged to work with the tournament on the player and fan experience and will have an emphasis on encouraging responsible drinking.
Six Nations CEO Benjamin Morel said: "We are absolutely delighted to enhance our long-standing relationship with Guinness and they will be a terrific title sponsor for Rugby's greatest championship. Guinness are world leaders and our partnership between two great iconic brands will enable us to reach new audiences on a global scale.
"We could not be more excited to be working with the Guinness team over the coming years on developing new and innovative ways to connect with our fans and consumers."