Casimiro or Casemiro may refer to:

• Casemiro do Amaral (1892–1939), Brazilian footballer
• Casemiro Mior (born 1958), Brazilian football manager and former footballer
• Casimiro de Abreu (1839–1860), Brazilian poet, novelist and playwright
• Casimiro Alegre (1741–1825), Argentine militia officer and landowner
• Casimiro Andrada, Filipino politician, mayor of Balasan
• Casimiro Asumu Nze (born 1975), Equatoguinean sprinter
• Casimiro Berenguer (1909–2000), Puerto Rican nationalist
• Casimiro Castro (1826–1889), Mexican painter and lithographer
• Casimiro Díaz (1693–1746), Spanish Augustinian friar
• Casimiro Gennari (1839–1914), Italian Catholic cardinal
• Casimiro Gómez Ortega (1741–1818), Spanish physician and botanist
• Casimiro Monteiro (1920–1993), Portuguese Goan assassin
• Casimiro Montenegro Filho (1904–2000), Brazilian army and air force officer
• Casimiro Olañeta (1795–1860), Bolivian politician
• Casimiro de Oliveira (1907–1970), Portuguese racing driver
• Casimiro Radice (1834–1908), Italian painter
• Casimiro Sainz (1853–1898), Spanish painter
• Casimiro Torres (1906-?), Chilean footballer
• Casimiro Ynares III (born 1973), Filipino politician
• Casimiro (streamer) (born 1993), Brazilian sports journalist and streamer

• Acácio Casimiro (born 1949), Portuguese footballer
• Augusto Casimiro (1889–1967), Portuguese journalist
• Bayani Casimiro (1918–1989), Filipino dancer
• Carlos Casimiro (born 1976), Dominican Republic baseball player
• Casemiro (born as Carlos Henrique Casimiro 1992), Brazilian footballer
• Didier Casimiro (born 1966), Russian businessman, a VP of Rosneft
• Fernando Casimiro (1931–2014), Portuguese sprinter
• Gisela Casimiro (born 1984), Portuguese writer and activist
• Henrique Casimiro (born 1986), Portuguese cyclist
• Isabel Casimiro, Mozambican sociologist
• Joaquim Casimiro (1808–1862), Portuguese composer and organist
• Julie Casimiro (born 1962), American politician
• Luis Casimiro, Spanish basketball coach
• Manuel Casimiro (born 1941), Portuguese painter