Pierre de Fermat was a French mathematician born in 1601, known for his contributions to number theory and probability. He is best recognized for Fermat's Last Theorem, which states that no three positive integers can satisfy the equation a^n + b^n = c^n for any integer value of n greater than 2. This theorem remained unproven for over 350 years until it was finally solved by Andrew Wiles in 1994. Fermat also made significant advancements in calculus and geometry, particularly through his work on the properties of curves and tangents. He is credited with developing the concept of infinitesimal calculus independently of Isaac Newton. Fermat's work laid the groundwork for many modern mathematical theories and continues to influence the field today.