The 24-year-old midfielder joins the Magpies for an undisclosed fee from Lyon, where he has been one of the outstanding performers in Ligue 1 over the past two seasons, and will wear shirt number 39 - the number of the taxi once driven by his father.
Born in Rio de Janeiro, Guimarães started out with Audax, where he made his debut as a 17-year-old, before moving on to Brazilian top-flight side Athletico Paranaense, where he won the Copa do Brasil and the Copa Sudamericana as well as being named in the Campeonato Brasileiro Série A team of the year in 2019.
He then signed for Lyon and, having won an Olympic gold medal with his country at the 2020 summer games, has earned three full caps for the Seleção. He is currently on international duty with Tite’s side and completed his medical in his homeland ahead of travelling to Newcastle next week, following Brazil's clash with Miguel Almiron's Paraguay on Wednesday.
Guimarães becomes head coach Eddie Howe's third signing of the transfer window, following England international Kieran Trippier and New Zealand international Chris Wood to St. James' Park.
Eddie Howe said: "Bruno is a hugely exciting talent and has been one of our primary targets so I'm delighted to secure him. He strengthens the group immediately ready for the challenge ahead.
"He has been one of the standout performers in France and is a full international for Brazil so I have no doubt our supporters will really enjoy watching him. We look forward to welcoming him to the club on his return from international duty."