  The US particle physics community planning exercise (a.k.a. Snowmass) is
organized every 7 to 9 years to provide a forum for discussions among the
entire particle physics community to develop a scientific vision for the future
of particle physics in the U.S. and its international partners. The Snowmass 21
Accelerator Frontier activities include discussions on high-energy hadron and
lepton colliders, high-intensity beams for neutrino research and for Physics
Beyond Colliders, accelerator technologies, science, education and outreach as
well as the progress of core accelerator technologies, including RF, magnets,
targets and sources. Here we summarize the Snowmass 21 discussions on future
HEP accelerator facilities.
