Alessandro Vespignani (born April 4, 1965) is an Italian-American physicist, best known for his work on complex networks, and particularly for work on the applications of network theory to the mathematical modeling of infectious disease, applications of computational epidemiology, and for studies of the topological properties of the Internet.

Together with Alain Barrat and Marc Barthelemy he has published in 2008 the monograph Dynamical Processes on Complex Networks.

He has collaborated with, among others, Luciano Pietronero, Benoit Mandelbrot, Betz Halloran, Ira Longini, and David Lazer.

He describes his current research as being focused on "interdisciplinary application of statistical and numerical simulation methods in the analysis of epidemic and spreading phenomena and the study of biological, social and technological networks.

[9] The modeling analysis mapped the early dispersal of infections and the temporal windows of the introduction of SARS-CoV-2 and onset of local transmission in Europe and the USA,[10] showing that hidden outbreaks were spreading almost completely undetected in major US cities.