Karl Theodor Wilhelm Weierstraß (often Karl Theodor Wilhelm Weierstrass in English texts) (1815 - 1897) German mathematician, the father of modern analysis.

Born in Ostenfelde, of a government official from Paderborn, young Karl showed an aptitude for mathematics but his father intended for him to follow in his footsteps to a career in public office. The son went to the University of Bonn to study law and economics but focused his attention on mathematics to the point of ignoring the requirements of the degrees his father intended him to obtain. Karl left Bonn for Münster and studied elliptic functions extensively. After being appointed chairman at an university in Berlin, Karl Weierstraß proved the fundamental calculus notion of the limit, regaining Bernard Bolzano's forgotten results in the famous Bolzano-Weierstraß theorem. Several other important calculus notions bear Weierstraß's name.