Benjamin Constant Botelho de Magalhães (18 October 1836 – 22 January 1891) was a Brazilian military officer and political thinker.

He left the Brazilian Positivist Society because of internal disagreements, but remained an ardent pupil of Comte until the end of his life.

His republican views led him to found the Clube Militar (or Military Club), with Deodoro da Fonseca, in May 1887.

[1] It was based in the Praia Vermelha Military School, and, shortly before his death, helped to organize a coup to overthrew Emperor Pedro II and establish a republic.

He was considered the founder of the Republic in the Constitution of 1891, having died earlier the same year in Rio de Janeiro, aged 54.