Louis Bachelier (1870-1946)

The French mathematician Louis Bachelier is attributed to have done the first theoretical work on Brownian Motion in his Ph.D. thesis entitled Théorie de la Spéculation (translated as The Theory of Speculation) in 1900.  This work is often overshadowed by the work of Albert Einstein done 5 years later of which Einstein was apparently unaware. Despite this, Bachelier's work is often considered to be more substantial in directly linking stochastic (random) processes such as Brownian motion to a mathematical framework. He established that such stochastic processes are well described by the Wiener distribution and thus formally tying Brownian motion to the diffusion equation.