EpiModel is an R package for simulating and analyzing mathematical models of infectious disease dynamic. The package provides a unified framework, supporting deterministic compartmental, stochastic individual contact, and stochastic network models. Standard templates for SI, SIR, and SIS disease types epidemics with and without demographics are also available. The package offers a flexible API for customizing and extending models. Network models use the robust statistical methods of exponential-family random graph models (ERGMs) from the Statnet suite of software packages in R.