Marvin Isadore Knopp (January 4, 1933 – December 24, 2011) was an American mathematician who worked primarily in number theory.

He received his PhD under Paul T. Bateman from the University of Illinois in 1958 where he became friends with fellow student Gene Golub.

[3] He is the father of pianist Seth Knopp, and of Yehudah, Abby, and Elana.

Marvin found happiness from his children, old movies, great music and numbers.

[6] In Jean Dieudonné's influential book A Panorama of Pure Mathematics (Academic Press, 1982), he is mentioned (p. 95) as one of those who "made substantial contributions" to the theory of modular forms.