Cândido Firmino de Mello-Leitão (July 17, 1886 – December 14, 1948) was a Brazilian zoologist who is considered the founder of Arachnology in South America, publishing 198 papers on the taxonomy of Arachnida. He was also involved with education, writing high-school textbooks, and contributed to biogeography, with essays on the distribution of Arachnida in the South American continent.