A modular buttstock system for firearms includes user replaceable and interchangeable buttstock modules. The modules include a comb portion and butt portion which may be provided in a variety of configurations, sizes, and materials. The modules and firearm buttstock each include complementary configured mounting portions and a mounting system designed to provide interchangeable and removable attachment of the modules to the buttstock. In some non-limiting embodiments, the buttstock and modules may be formed of synthetic materials.