Adriaan Cornelis "Aad" Zaanen (14 June 1913 in Rotterdam – 1 April 2003 in Wassenaar) was a Dutch mathematician working in analysis.

He studied Stefan Banach's Théorie des Opérations Linéaires, the book that laid the foundations of functional analysis, and Marshall H. Stone's Linear Transformations in Hilbert Space.

During this period he wrote nine scientific papers on integral equations with symmetrisable kernels that were published in the Proceedings of the Royal Netherlands Academy of Arts and Sciences in 1946-47.

There he started a large research programme into the theory of Riesz spaces, together with his first doctoral student Wim Luxemburg, Professor of Mathematics at the California Institute of Technology.

[7] He is however best known for four large books that each took a prominent place in scientific literature: Zaanen was elected a member of the Royal Netherlands Academy of Arts and Sciences in 1960.