Many nearshore and offshore structures are supported by vertical piles to elevate them beyond the reach of water and waves. In addition to carrying the axial load from the weight of the structure, piles must also resist horizontal forces induced by waves which may lead to bending and shear stresses within the pile and its foundation. This chapter will introduce methods for the estimation of forces on vertical piles imparted by linear and nonlinear waves, across both nonbreaking and breaking