Howe takes over from Graeme Jones, who has been in interim charge following the departure of Steve Bruce last month.
The 43-year-old arrives at St James' Park having taken previous club AFC Bournemouth for whom he made more than 300 appearances as a player, from League Two to the Premier League across two spells over a period of 11 years.
"It is a great honour to become head coach of a club with the stature and history of Newcastle United," Howe told the club’s official website. "It is a very proud day for me and my family.
"This is a wonderful opportunity, but there is also a lot of work ahead of us and I am eager to get on to the training ground to start working with the players."
Howe guided AFC Bournemouth into the Premier League for the first time in their history in 2015/16, only seven years after first taking over as manager and steering them to safety in League Two despite a 17-point deduction.
Newcastle are in 19th place with five points from 11 matches, level on points with bottom club Norwich City.
Howe's Premier League debut as Newcastle boss will come at home to Brentford on Saturday, 20 November, 2021.
