Casemiro is "as determined as ever" to win trophies with Manchester United following confirmation of his transfer from Real Madrid.
United confirmed last week an agreement had been reached with Madrid, and the reported £60million (€70m) deal officially went through on Monday.
The 30-year-old bade an emotional farewell to Madrid at a news conference prior to travelling to Old Trafford for United's clash with fierce rivals Liverpool.
And after being paraded on the pitch ahead of kick-off, United announced on their website that Casemiro has penned a four-year deal with the option of a further 12 months.
Vastly experienced Brazil international Casemiro won 18 trophies in his decade with Madrid, including five Champions Leagues, and is eager to land more silverware in England.
"The opportunity to start a new challenge at Manchester United and in the Premier League is extremely exciting," he said.
"I've worked with many great managers in my career, and having met with Erik [ten Hag] and heard his ideas, I can't wait to work closely with him, his staff and my new team-mates in the coming years.
"I'm ending one beautiful journey in Madrid whilst starting another in Manchester as determined as ever to win football matches, win trophies and make our fans proud by bringing success to this great club.
"Everybody knows the history of Manchester United, the significance of the club around the world and what it means to its supporters.
"To represent United is an honour and I am ready to give everything to help the team achieve our ambitions."
Casemiro has played over 550 games in his career and has 22 trophies to his name, including Copa America success with Brazil, whom he is expected to represent in this year's World Cup.
He becomes United's fourth signing of the window following the arrivals of Lisandro Martinez, Tyrell Malacia and Christian Eriksen.
"Casemiro is a serial winner and one of the best midfielders in world football; his exceptional record speaks for itself," said United football director John Murtough.
"He compliments the skillsets of the squad and will be a great addition to the dressing room with his experience, knowledge and character.
"I know that Casemiro remains as determined as ever to be successful on the pitch and we look forward seeing that happen in a Manchester United shirt."