The NHL Board of Governors voted unanimously in favour of awarding Seattle the league's 32nd franchise on Tuesday.
The NHL had been at 30 teams since 2000 before deciding to expand to Las Vegas in 2016.
The 2021 NHL Expansion Draft will be under the same rules for Seattle as the Vegas Golden Knights in 2017.
Seattle's ownership group sent a strong contingent to Georgia for the board of governors meetings, including majority owner David Bonderman, Hollywood producer Jerry Bruckheimer and CEO Tod Leiweke, who most recently worked as the NFL's COO before he resigned in March 2018.
Seattle has a lot going for it, including some semblance of a hockey culture as a longtime home to multiple WHL franchises in the area.
The Seattle franchise will be added to the Pacific Division in the Western Conference in 2021-22, with the Arizona Coyotes moving to the Central Division. The Seattle Metropolitans were the first American team to win the Stanley Cup, defeating the Montreal Canadians in 1917.
As the 32 team, the arrival of Seattle allows the NHL to finally balance out the league's four divisions.
"Seattle's one of the fastest-growing cities in the country", NHL Commissioner Gary Bettman said recently. Seattle can not buy out players chosen in the Expansion Draft earlier than the summer following its first season.
KeyArena is now undergoing a multi million dollar renovation.
With the expansion, the $800 million Seattle Arena expansion project will break ground on Wednesday.
With a metro population of approximately 3.8 million people, Seattle was the largest city in the United States without both an National Hockey League and an NBA team since the Sonics left for Oklahoma City in 2008.
The board's nine-member executive committee recommended proceeding with the expansion application back in October after a presentation that included Bonderman, Bruckheimer and Leiweke.