This letter presents a novel superstrate composed of multilayer metasurface (MM), which is characterized by wideband monostatic and bistatic radar cross section reduction (RCSR) for Fabry–Perot (FP) antenna with magnetoelectric (ME) dipole-fed. The proposed MM consists of four layers, the top three layers form a polarization-selective absorber (PSA), and the bottom layer is a polarization conversion metasurface (PCM). The copolarized incident waves are absorbed by the PSA, while the cross-polarized waves pass through with a low insertion loss. Then, it is reflected by the PCM with 90° polarization rotation and absorbed by the upper PSA. Additionally, the bottom layer of the PCM unit is an improved pattern instead of the ground plane. It is capable of polarization conversion and partial reflection. Therefore, the MM and ME dipole are respectively utilized as the partially reflecting surface (PRS) and the primary source to construct an FP antenna. Simulation and measurement results show that the bandwidth of monostatic RCSR is more than 80%. The FP antenna also achieves a high aperture efficiency of 51%, which is due to the benefit from the widebeam characteristics of the ME dipole.