This chapter will provide an overview of mobility management principles for fifth generation (5G) new radio (NR) in E-UTRA-NR DC with evolved packet system (EPS) and next generation RAN (NG-RAN) in 5G System. It will touch on the new requirements and challenges such as flexible mobility that must be met by 5G System with respect to mobility management. It also provides a detailed overview of radio resource control protocol (RRC) and non-access stratum (NAS) states, handover and mobility procedures in the various states, also beam management, beam level, and cell level mobility, handover procedures for Non-Standalone and Standalone mode. In addition, it provides insights on challenges due to high mobility and requirements to support ultra-reliable low latency with respect to mobility. Furthermore, it outlines the procedures for inter-system mobility. Finally, it gives an outlook for supporting enhanced mobility features in subsequent third generation partnership project (3GPP) releases.