"This is a fantastic opportunity, but we have a lot of work ahead of us and I am eager to get out on the training ground and start working with the players," said Howe.
The 43-year-old Englishman left Bournemouth this summer after several successful years as both player and later coach at the club.
Now he will try to save Newcastle still in the English top division.
The team is second to last in the Premier League, with five recorded points in eleven matches.
In early October, Newcastle was bought by the Saudi investment fund PIF.
Two weeks later, then-coach Steve Bruce was fired.