Hosted by The Society for Modeling and Simulation International (SCS), the Annual Modeling and Simulation Conference (ANNSIM) is a new annual conference after merging SpringSim and SummerSim into a single conference starting in 2021. ANNSIM 2021 will be a hybrid event. It is the flagship conference of SCS to cover state-of-the-art developments in Modeling & Simulation (M&S). We invite original contributions to the theory and practice of modeling and simulation in any scientific or engineering discipline. The conference includes keynote speeches presented by technology and industry leaders, technical sessions, professional development tutorials, as well as vendor exhibits. Scientists, engineers, managers, educators, and business professionals who develop or use M&S methodologies and tools are invited to participate and present original contributions. The technical proceedings of SCS will be listed in the ACM and IEEE digital libraries. Call For Papers: https://scs.org/wp-content/uploads/2020/12/SC16341_AnnSim21_v7.pdf.