In this chapter we consider plane, symmetric, orthotropic rectangular laminates under inplane compressive and biaxial loading, which are simply supported at all edges, and determine the critical buckling loads of these laminates wherein we assume Classical Laminated Plate Theory (CLPT) to be valid. This type of analysis is also referred to as a Navier solution. The considerations are later extended to unsymmetric cross-ply laminates and angle-ply laminates. Navier solutions are also considered in the context of First-Order Shear Deformation Theory (FSDT).