In this talk, I will present an overview of the numerical models that have been developed during the last few years for the performance prediction of America's Cup yachts. Different aspects which characterize the behaviour of racing boats will be discussed, such as the role of the yacht appendages, the dynamical response of the yacht in calm and wavy seas and the fluid-structure interaction between wind and sails. A selection of the large scale numerical simulations that were performed to support an America's Cup design team during the last three campaigns will be presented, highlighting the role played by the numerical simulations in the overall yacht design process.