'It is a great honour to become head coach of a club with the stature and history of Newcastle United. It is a very proud day for me and my family,' Howe said.
'This is a wonderful opportunity, but there is also a lot of work ahead of us and I am eager to get onto the training ground to start working with the players.
'I would like to thank the club's owners for this opportunity and thank the club's supporters for the incredible welcome they have already given me. I am very excited to begin our journey together.'
Howe is perhaps a surprising choice to lead what is now the richest club in the world following the recent £305million takeover, with the new owners enjoying the financial might of Saudi Arabia's Public Investment Fund, which is worth over £300billion. The club will be able to spend some of those funds for the first time in January amid a fierce battle against relegation.
His name did not have the backing of all members close to the new consortium when first floated four weeks ago, with Unai Emery becoming the clearly favoured candidate - but the Spaniard rejected an approach and has stayed on at Villarreal.
Amanda Staveley, however, was always keen to speak with Howe and he was interviewed two weeks ago. Some of his former Bournemouth players in the Newcastle dressing-room - which include Callum Wilson, Ryan Fraser and Matt Ritchie - had already communicated their support for their old boss to Staveley.
Sportsmail understands Howe would also have been the man the previous ownership turned to had Steve Bruce been sacked on their watch. Lee Charnley - the managing director who remains at the club - is thought to have supported Howe's cause in light of the takeover.