Future high-energy colliders are discussed, in particular lineare+e−colliders,&mgr;+&mgr;−colliders and hadron colliders. The energies of thee+e−colliders are larger than that of the existinge+e−collider LEP. The energies of the very large hadron colliders are larger than that of the LHC being constructed at CERN. Two&mgr;+&mgr;−colliders at 100 and 3000 GeV are included. For all these colliders, parameter lists, topics of R&D, and progress with component tests are discussed. ©2001 American Institute of Physics.