Pierre de Fermat is an exceptional figure in the history of science: being a lawyer by profession, he devoted only his free hours to mathematics. His scientific legacy is largely preserved in the form of letters exchanged with other luminaries of his time, such as Marin Mersenne, Blaise Pascal or René Descartes. The genius of this French scientist, despite his amateurism, manifested itself in various fields: in probability theory, mathematical analysis and especially in number theory, within which he put forward a hypothesis that puzzled the most important mathematicians for more than three centuries. The story of solving the problem known as Fermat's Last Theorem can be called one of the most beautiful legends of the scientific world.