To withstand the challenging conditions of increased luminosity and higher pileup expected
during the high-luminosity LHC (HL-LHC), the muon spectrometer of the CMS experiment will
undergo specific upgrades targeting both electronics and detectors. The goal is to cope with
the new challenging data-taking conditions of HL-LHC and to improve the present tracking and
triggering capabilities. The electronics upgrades will target the existing Drift Tubes (DT) in the
Muon central barrel section, Cathode Strip Chambers (CSC) in the Muon end-cap sections, and
Resistive Plate Chambers (RPC) in the Muon barrel and end-cap sections. New detector stations
will be deployed in the Muon end-caps where the background rate is expected to be higher. The
detector upgrades are based on triple gas electron multiplier (GEM) and improved RPC (iRPC)
technologies, featuring improved time and spatial resolutions, and enhanced rate capability. In
this paper an overview of the Muon System upgrades, ongoing activities, and plans are presented.