Abstract: In this article, we present a meshless method based on the method of fundamental solutions(MFS) capable of solving free surface ﬂow in three dimensions. Since the basis function of theMFS satisﬁes the governing equation, the advantage of the MFS is that only the problem boundaryneeds to be placed in the collocation points. For solving the three-dimensional free surface withnonlinear boundary conditions, the relaxation method in conjunction with the MFS is used, in whichthe three-dimensional free surface is iterated as a movable boundary until the nonlinear boundaryconditions are satisﬁed. The proposed method is veriﬁed and application examples are conducted.Comparing results with those from other methods shows that the method is robust and provides highaccuracy and reliability. The eﬀectiveness and ease of use for solving nonlinear free surface ﬂows inthree dimensions are also revealed.