Former Norwegian Premier Jens Stoltenberg will take over as NATO chief starting in October, the second Scandinavian in a row to lead the military alliance.
Friday's announcement comes at a critical time as the crisis over Ukraine and Crimean Peninsula has suddenly made the 28-nation alliance a more important security force in Europe.
Stoltenberg called the crisis with Russia over Ukraine "a brutal reminder of how important NATO is."
"I want to express my support that NATO does not accept the changing of borders by force within Europe," he said in Oslo. "NATO has once again proven its relevance."
NATO Secretary General Anders Fogh Rasmussen, who took up the role in 2009, will step down after a NATO summit in Wales later this year.
"Warm congratulations," the Dane said in a Twitter message Friday to his fellow Scandinavian politician, who was confirmed during a meeting of NATO's council of ambassadors.
The top military job at the alliance, now held by Gen. Philip Breedlove, is traditionally a position for an American.
In Washington, the White House welcomed Stoltenberg's appointment, praising him as a "proven leader with a demonstrated commitment to the trans-Atlantic alliance."
Norwegian Prime Minister Erna Solberg, who replaced Stoltenberg as prime minister last year, said the alliance was getting "a strong and unifying secretary general."
A two-time prime minister, Stoltenberg became a recognizable face on the international scene with his dignified response to the twin terror attacks that killed 77 people in Norway in July 2011.
Despite his and Norway's dovish reputation, Stoltenberg pushed through an increase in military spending throughout his second spell as prime minister between 2005 and 2013.
And he has always been a staunch NATO ally. He endorsed President George W. Bush's war on terror after the Sept. 11, 2011 terror attacks in the U.S., and backed the decision to send troops into Afghanistan where they remained throughout his leadership.
He also backed the alliance's bombing campaign over Libya that helped oust Moammar Gadhafi in 2011.
Lewis contributed from Oslo. Jan M. Olsen also contributed from Copenhagen.
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