Renowned for the clarity and comprehensibility of his textbooks, Ernst Leonard Lindelöf distinguished himself as a mathematician with his research on and function theory. His work became the basis for the study of mathematics history in his native land.

Lindelöf, the son of a professor of mathematics, was born in Helsingfors, Sweden (now Helsinki, Finland) on March 7, 1870. Interested in mathematics and science from a young age, he studied at his father's university from 1887 to 1900, although he took breaks during that period to study at prestigious schools in Stockholm, Paris, and Göttingen, Germany. In 1890, while only twenty, Lindelöf published his first professional paper, which outlined solutions for differential equations. After receiving his degree at Helsingfors in 1895, Lindelöf stayed on to continue his studies and teach mathematics classes as a private tutor.

Soon recognizing the talent of the young mathematician, the university gave Lindelöf a post as assistant professor in 1902, promoting him only a year later, impressively, to full professor of mathematics. By then, Lindelöf's reputation as a mathematician had been firmly established in the academic world. In the meantime, he had decided to abandon any ambitions for creative scientific research in favor of his responsibilities as a professor.

In 1905 Lindelöf published Calculation of Residues and Their Application to Function Theory, which analyzed the role of residue theory as applied to function theory. The book was well received, both because of its brilliant content and its accessibility and lucidity.

Beginning in 1907, Lindelöf served as a member of the editorial board for Acta Mathematica. In the latter part of his career, he devoted himself to writing textbooks. Among these were the four-volume Differential and Integral Calculus and Their Application (1920-1946) and An Introduction to Function Theory (1936). Lindelöf died in Helsinki on June 4, 1946.