Carlos Henrique Casimiro (born 23 February 1992), known as Casemiro, is a Brazilian professional footballer who plays as a defensive midfielder for Premier League club Manchester United and the Brazil national team. He is widely regarded as one of the best defensive midfielders in the world and of all time.

Formed at Sao Paulo, where he scored 11 goals in 111 official games, Casemiro moved to Real Madrid in 2013, and also spent 2014–15 on loan at Porto. He was part of the Real Madrid squad that won four Champions League titles in five seasons, from 2014 to 2018. In total he won fifteen major trophies at Real Madrid, including five Champions Leagues, three La Liga titles, one Copa del Rey and three FIFA Club World Cups. In 2022, he left Real Madrid to sign with Manchester United.

A full international since 2011, Casemiro was in Brazil's squad at the 2018 FIFA World Cup as well as four Copa America tournaments, winning the 2019 edition.

Casemiro mainly plays as a defensive midfielder, although he has also been deployed in a box-to-box role in the centre of the pitch, or even as a centre-back on occasion. While he is not particularly talented or skilful from a technical standpoint (although he was able to improve in this area under manager Zinedine Zidane during their time at Real Madrid together), Casemiro is an intelligent, physically strong, mobile, aggressive, and hard-tackling midfielder, with an extremely high work-rate. While he is mainly known for his ability to provide balance to his teams by supporting his more offensive-minded teammates defensively, and distributing the ball to them accurately after winning back possession, he is also a well-rounded midfielder, who possesses a powerful shot from outside the penalty area, and reliable distribution, as well as an ability to get forward with his runs off the ball, or start attacks with his passing. These characteristics also enable him to contribute offensively, or even score goals, in addition to breaking up plays. Moreover, his quick reactions, as well as his excellent positional sense, ability to read the game, and good anticipation, enable him to excel in a holding midfield role in front of the defence, by cutting out counter-attacks and shielding the back-line.

Often described as a "destroyer" in the media, he has drawn praise from pundits for his energetic and combative style of play, as well as his tactical awareness and abilities as a ball winner, which enable him to cover ground, track back, and press opponents. His tenacity on the pitch, exemplified by his fierce challenges and stamina, have led Marca to nickname him "The Tank." In addition to his footballing abilities, he also stands out for his competitive spirit, mentality, consistency, and determination on the pitch. Despite maintaining a good disciplinary record, he has, however, also come into criticism in the media at times over his excessively aggressive challenges on the pitch. Casemiro's playing style has drawn comparisons with that of former Real Madrid defensive midfielder Claude Makelele, as well as compatriot Toninho Cerezo.