Born in Düren, Germany, I first learned mathematics from Georg Ohm at the Jesuit gymnasium in Cologne then had Simeon Poisson and
Joseph Fourier as my doctoral advisors.
My first published paper was a partial proof for the case n = 5 for Fermat's last theorem (completed later by Legendre), and later I provided a full proof for n = 14 on my own.
One big claim to fame (or honor?) is that as a professor I filled the vacant chair of Carl Friedrich Gauss upon his death.
As a teacher, I mentored many great students in mathematics, such as Gotthold Eisenstein, Leopold Kronecker, and Rudolf Lipschitz.
I am credited with the modern formal definition of a function, which was a big step in mathematics.
Showing my diversity in mathematics, my eponymic attributions abound: a diophantine approximation theorem, a theorem on arithmetic progressions and prime numbers, a unit theorem in algebraic number theory, a beta function, conditions in Fourier series,a probability distribution, a series in analytic number theory), stability criterion in dynamical systems, a tessellation (also known as a Voronoi diagram), and a boundary condition in differential equations, etc.
As a final big claim to fame, my brain is preserved in the department of physiology at the University of Göttingen along with the brain of Gauss.
Answer:
Lejeune Dirichlet (1805  1859)
