A semiconductor package includes a package substrate, an interposer on the package substrate, a plurality of semiconductor devices on the interposer and spaced apart from each other, the semiconductor devices being electrically connected to the interposer, a dam structure on the interposer extending along a peripheral region of the interposer, the dam structure being spaced apart from the semiconductor devices, and a stress relief on the interposer, the stress relief including an elastic member that fills gaps between the semiconductor devices and the dam structure.