The Welsh team, who hammered Ireland 25-7 to claim a first Grand Slam since 2012, will be coached by New Zealander Wayne Pivac for the next Six Nations, with Warren Gatland set to step down after the 2019 World Cup in Japan.
The champions have a tough Six Nations schedule next season, with trips away to last year's champions Ireland and this year's runners-up England in the second and fourth rounds respectively.
Ireland host Scotland on the opening weekend while England travel to France. England, who drew 38-38 against Scotland in a stunning Calcutta Cup finale, play two home games next year -- against Ireland and Wales -- in the third and fourth rounds.
Head coach Warren Gatland and Jonathan Davies during the celebration for Wales' Six Nations victory at the National Assembly for Wales on March 18, 2019 in Cardiff, Wales.
Image credit: Eurosport
"The 2019 Championship gave us a stunning finale with three teams competing for the title on the final weekend, a brilliant Grand Slam winner and a unique Calcutta Cup match to finish the Championship off," said Six Nations CEO Ben Morel.
We look forward to developing the championship in partnership with our (rugby) unions, sponsors and ... our fans over the coming years, and to the next two years of the Guinness Six Nations Championship generating even more excitement than the 2019 edition.
Italy's annual participation in the championship was questioned this month, with England coach Eddie Jones suggesting that the Six Nations should consider relegation after Italy lost 21 matches in a row.
England will open their 2021 Six Nations campaign against Scotland while Wales will start with a home game against Ireland.