Louis Welles Shapiro (born 1941)^[1] is an American mathematician working in the fields of combinatorics and finite group theory. He is an emeritus professor at Howard University.^[2]

Shapiro attended Harvard University for his undergraduate studies and then the University of Maryland, College Park for graduate school.^[3] Shapiro is most known for introducing the Riordan array, named after mathematician John Riordan,^[4] and developing the theory around it. He has been an organizer of and speaker at the annual International Conference on Riordan Arrays and Related Topics,^[5][6] which has been held annually beginning 2014.