  The potential of muon beams for high energy physics applications is described
along with the challenges of producing high quality muon beams. Two proposed
approaches for delivering high intensity muon beams, a proton driver source and
a positron driver source, are described and compared. The proton driver
concepts are based on the studies from the Muon Accelerator Program (MAP). The
MAP effort focused on a path to deliver muon-based facilities, ranging from
neutrino factories to muon colliders, that could span research needs at both
the intensity and energy frontiers. The Low EMittance Muon Accelerator (LEMMA)
concept, which uses a positron-driven source, provides an attractive path to
very high energy lepton colliders with improved particle backgrounds. The
recent study of a 14 TeV muon collider in the LHC tunnel, which could leverage
the existing CERN injectors and infrastructure and provide physics reach
comparable to the 100 TeV FCC-hh, at lower cost and with cleaner physics
conditions, is also discussed. The present status of the design and R&D efforts
towards each of these sources is described. A summary of important R&D required
to establish a facility path for each concept is also presented.
