The ergm.sign package is an implementation of the exponential random graph model (ERGM) for signed networks. It builds on the statnet packages and provides the ability to fit an ERGM to static signed networks or a temporal exponential random graph model (TERGM) to dynamic signed networks. It also includes functions for the descriptive analysis, simulation, and evaluation of the model fit. In this paper, we illustrate the signed exponential random graph model and its implementation in the ergm.sign package using data on tribal and rebel conflicts.