FRED (A Framework for Reconstructing Epidemiological Dynamics) is a flexible agent-based modeling framework created by the Public Health Dynamics Laboratory at the University of Pittsburgh, in collaboration with the Pittsburgh Supercomputing Center and the Carnegie Mellon University School of Computer Science. FRED supports research on infectious disease epidemics dynamics and the interacting effect of mitigation strategies, personal health behavior, and viral evolution. FRED uses census-based synthetic populations; synthetic populations for the United States that are compatible with FRED are available on the FRED website. FRED is distributed as C++ source code with Python and Perl scripts. FRED can be compiled and run on MacOS and Linux; FRED has also been tested on Windows running Cygwin.