Einar Hille (birth name Carl Einar Hille) was an American mathematician, born 28 June 1894 in New York, USA, and died 12 February 1980 in La Jolla, California.

Hille's main work was on integral equations, differential equations, special functions, Dirichlet series and Fourier series. Later in his career his interests turned more towards functional analysis.

His name persists among others in the Hille-Yosida theorem.

Hille was married to Kirsti Hille, sister of mathematician Øystein Ore, and had two sons, Harald and Bertil Hille.

Second Edition. This famous work is a textbook that emphasizes the conceptual and historical continuity of analytic function theory. The second volume broadens from a textbook to a textbook-treatise, covering the ``canonical'' topics (including elliptic functions, entire and meromorphic functions, as well as conformal mapping, etc.) and other topics nearer the expanding frontier of analytic function theory. In the latter category are the chapters on majorization and on functions holomorphic in a half-plane.