This paper aims to present an optimization method for very-high-speed electrical machines based on multiphysical analytical models. Analytical models allow a fast design but have to be robust and reliable. The set of models presented is very complete and covers the mechanical design of the rotor, the computation of the losses and the computation of the back EMF and torque constants. All the models have been validated on a 400 krpm prototype, which is, to the authors’ knowledge, one of the smallest and fastest electrical motor ever operated. Several optimization scenarios are presented and analyzed to get the best performance of very-high-speed machines.