Ronald Fisher

British statistician and geneticist who single-handedly invented or developed much of modern statistics — analysis of variance, maximum likelihood, experimental design — while also contributing to the synthesis of Mendelian genetics with Darwinian evolution.

Created the modern statistical toolkit — ANOVA, p-values in experimental context, maximum likelihood estimation, Fisher's exact test — that underlies virtually all empirical research in biology, medicine, and social science, while simultaneously being one of the primary architects of the modern evolutionary synthesis.