Neil J. Calkin (born 29 March 1961) is a professor at Clemson University in the Algebra and Discrete Mathematics group of the School of Mathematical and Statistical Sciences. His interests are in combinatorial and probabilistic methods, mainly as applied to number theory. Together with Herbert Wilf he founded The Electronic Journal of Combinatorics in 1994. He and Wilf developed the Calkin–Wilf tree and the associated Calkin–Wilf sequence.