Lebesgue, who was born at Beauvais in northern France, studied at the Ecole Normale Supérieure. He obtained posts at Rennes (1902) and Poitiers (1906) universities, at the Sorbonne (1910), and at the Collège de France (1921).

Lebesgue's extremely important contributions to measure theory and the theory of integration were stimulated by the earlier work of Emille Borel and by Camille Jordan's famous Cours d'Analyse (Lessons in Analysis). The importance of Lebesgue's work resides in the fact that he was the first mathematician to develop integration in a measure- theoretic context. This allowed natural generalizations of both concepts to be made. Lebesgue's definition of integral is considered, in many respects, smoother and more useful than those that came before.

Lebesgue also worked on the theory of point sets, the calculus of variations, and dimension theory. He wrote a very large number of books and papers and had interests in the pedagogy and history of mathematics.