Castellani is a surname of Italian origin meaning 'castellan'. Notable people with the name include:

• Aldo Castellani (1874–1971), Italian pathologist and bacteriologist
• Andrea Castellani (born 1972), former Italian rugby union player
• Bruto Castellani (1881–1933), Italian film actor of the silent era
• Carlo Castellani (1909–1944), Italian footballer
• Cesar Castellani (died 1905), Maltese architect
• Christopher Castellani (b. 1972), American novelist
• Daniel Castellani (b. 1961), Argentine volleyball player
• Daniela Castellani (born 1975), Italian softball player
• Enrico Castellani (1930–2017), Italian artist
• Giovanni Castellani (1888–1953), Italian archbishop and Vatican diplomat
• Giulio Giacomo Castellani (1619–1694), Roman Catholic Bishop of Cagli
• Gonzalo Pablo Castellani (born 1987), Argentine footballer
• Ines Castellani Fantoni Benaglio, also known by the pseudonym of Memini (1849–1897, Azzate), Italian writer
• Iván Castellani (born 1991), Argentine volleyball player
• John Castellani (1926–2021), American basketball player
• Leonardo Castellani (1899–1981), Argentine author, poet, and theologian
• Leonardo Castellani (engraver) (1896–1984), Italian engraver mainly active depicting landscapes with chalcography
• Mario Castellani (1906–1978), Italian comic actor
• Massimo Castellani (born 1961), Italian diver
• Michel Castellani, French politician
• Raymond Castellani (born 1933), American actor and founder of the Frontline Foundation
• Renato Castellani (1913-1985), Italian film director and screenwriter
• Rocky Castellani (b. 1926), American boxer
• Rudolph J. Castellani (b. 1964), American neuropathologist
• Ryan Castellani (b. 1996), American baseball player
• Stefano Castellani (born 1992), Italian footballer
• Valentino Castellani (b. 1940), Italian professor and politician; mayor of Turin 1993–2001